JP3235941B2 - Printer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer for forming an image such as a character or a graphic on a recording medium, and more particularly to a printer capable of monitoring a power supply state of an external host device.

[0002]

2. Description of the Related Art Conventionally, printers such as serial dot printers are roughly classified into a built-in type integrated with a host device such as a word processor and an external type connected to a separate host device by a signal cable. . The built-in printer is
Generally, the power supply circuit is shared, and when the host device is turned off, the printer device is automatically turned off. On the other hand, an external type printer has a dedicated power supply circuit built in, and the power operation of the host device and the power operation of the printer must be performed separately. Even if the host device is turned off, the printer automatically turns off. do not become.

In many cases, the printer is operated in an online mode operated by a command from a host device, and a user rarely operates the printer directly. For this reason, when the power of the host device is turned off, the user often forgets to turn off the power of the printer, which is not preferable in terms of energy saving.

As a prior art for solving such a problem, a data terminal device (Japanese Patent Laid-Open No.
7-155633) and a printer device (Japanese Unexamined Patent Publication No.
No. 354017).

FIG. 9 is a block diagram showing an example of an electrical configuration of a conventional printer. This printer device
CPU (Central Processing Unit) 51 for managing the operation of the entire apparatus
A ROM (read only memory) 52 which is a nonvolatile memory, a RAM (random access memory) 53 capable of rewriting data, an interface (I / F) 57 for connecting to the external host device 50, Panel unit 58 incorporating signal input means such as operation switches and signal display means such as display LEDs (light emitting diodes) and buzzers.
And an image forming unit 59 for forming an image on a recording medium
And a control circuit 54 for controlling the image forming section 59.

[0006] The CPU 51 performs signal processing such as data input / output, data transfer, and calculation according to a program stored in the ROM 52. The ROM 52 stores programs and data necessary for the operation of the CPU 51, and data necessary for printing such as character codes and character fonts. RAM5
Reference numeral 3 is used for a work area of the CPU 51, temporary storage of data received from an external host device, expansion of document data, and the like. The interface 57 exchanges data with an external host device. Such CPU 51, ROM
52, RAM 53, interface 57, panel unit 58
The control circuit 54 is mutually connected by a bus BUS including an address bus, a data bus, a control bus, and the like. Further, a clock circuit (not shown) for generating a clock signal 66 for determining an operation timing is built in the CPU 51, and is also supplied to the control circuit 54.

The image forming section 59 has a drive section 56 and a drive circuit 55. The drive unit 56 includes a print head that prints on a recording medium and a carriage (C
A drive unit such as a CR motor that transports R) in the width direction of the recording medium and a PF (paper feed) motor that transports the recording medium by a fixed amount. The drive circuit 55
Image forming section 59 based on a control signal from control circuit 54
Are driven.

The printer includes a logic power supply 61 for supplying power to a logic circuit for handling digital signals.
And a drive power supply 60 for supplying electric power to a unit requiring relatively large electric power, such as a motor, are connected to a commercial power supply without a switch or the like. The drive power supply 60 is connected to the image forming unit 59 via a power supply line Vcc3.
Power.

On the other hand, the logic power supply 61 is, for example, TTL
And a DC 5V suitable for CMOS and CMOS is output to a power supply line Vcc1, and supplied to a CPU 51, a ROM 52, a RAM 53, an interface 57, a panel unit 58, a control circuit 54, and a power supply disconnecting circuit 62 including a relay and the like. Also,
A part of the power supply line Vcc1 becomes a power supply line Vcc2 via a power supply cutoff circuit 62, and is connected to a panel part 58 and a part of the control circuit. Power-off circuit 62
Supplies power to the power supply line Vcc2 when the power saving signal 67 from the control circuit 54 is at a high level, and shuts off power supply to the power supply line Vcc2 when the power saving signal 67 is at a low level.

FIG. 10 is a block diagram showing an example of the interface 57. The external host device 50 and the interface 57 are connected via a connector 71. Here, a parallel interface system such as Centronics compliant is used, and data signals Data1 to Data8 (positive logic) are used as representative signal lines. ), A busy signal BUSY (positive logic), a strobe signal STROBE (negative logic), an acknowledge signal ACK (negative logic), and the like.

The data latch circuit 72 has a data signal Da.
The print code and print control code transmitted from the external host device 50 via ta1 to ta8 are stored in units of 8 bits, and the data is latched when the strobe signal falls. The busy flag 73 is constituted by a flip-flop or the like, and becomes a high level at the falling of the strobe signal.
The signal is output as it is to the external host device 50 as it is, and is taken into the CPU 51 via the general-purpose input / output circuit (I / O) 74. The external host device 50 constantly monitors the busy signal, and waits for the next data transmission until it goes low. Data latch circuit 72
Is latched by the CPU 51 via the bus, the CPU 51 outputs a clear signal CLEAR via the general-purpose input / output circuit 74 to invert the busy flag 73 to a low level. Note that the CPU 51 has a timer TA for measuring time.

FIG. 11 is a circuit diagram showing an example of a connection system between the external host device and the printer device. The power supply of the external host device is turned off and the equivalent of input signals when the printer device is energized. It is a figure showing a circuit. The external host device 50 and the printer device are connected via a connector 71, and an input buffer Q is provided on the input side of the interface 57.
1 (for example, TTL-IC model number “LS14”). Each signal line is connected to a power supply line (for example, 5 V) by a pull-up resistor R1 (for example, 1.5 kΩ to 4.7 kΩ) to prevent noise. Similarly, also on the output side of the external host device, pull-up resistors and pull-down resistors are connected to each signal line, and these can be represented by a combined impedance Z in an equivalent circuit.

Therefore, when the external host device is energized, the voltage level of the signal line is stabilized at the high level or the low level by the output from the external host device. When not connected to an external host device, the signal line is stabilized at a high level by the presence of the pull-up resistor R1. However, when the external host device is not energized and the printer device is energized, FIG.
As shown in FIG. 1, the output side of the host device can be regarded as being grounded through the combined impedance Z. Therefore, since the voltage level of the signal line is determined by the voltage division ratio of the pull-up resistor R1 and the combined impedance Z, the voltage level is an intermediate value between the high level and the low level.

FIG. 12A is a graph showing an example of a voltage change of the strobe signal. When the external host device is not transmitting data while the external host device 50 is connected to the printer device, the strobe signal is held at a high level (5 V in FIG. 12). When the power supply of the external host device is turned off in this state, the voltage level of the signal decreases exponentially as the power supply voltage decreases, and the intermediate potential determined by the voltage division ratio of the pull-up resistor R1 and the combined impedance Z (FIG. 12). At about 1.8V). Next, when the external host device is energized again, the signal level rises from the intermediate potential to the high level and stabilizes at a constant voltage.

As described above, when the external host device is off, since the combined impedance Z has a constant value, the intermediate potential generally falls within the range of 1.5 V to 4 V. When the input buffer Q1 is a TTL-IC,
The low level threshold is 0.8V to 1.1V. Therefore, even when the external host device is turned off, the strobe signal does not become low level, so that a situation in which the printer device receives data by mistake can be avoided.

FIG. 12B is a graph showing another example of a voltage change of the strobe signal. Some external host devices 50 output a low level (approximately 0.2 V in FIG. 12) momentarily when the power is turned on or off. This is presumably due to the fact that the power-on reset operates when the power of the external host device is turned on or off, and the strobe signal is momentarily set to the low level at that time. Looking at the waveform shown in FIG. 12B, it is difficult to distinguish the waveform from the strobe signal received by the printer device at the time of normal data transfer. Received data.

In particular, when the power of the external host device is turned off, the waveform of the strobe signal drops to near 0 V,
On the other hand, it is rising rapidly. This pulse width depends on the power supply capacity of the external host device and the characteristics of the output buffer, but may take several hundreds of microseconds. Further, the voltage change curve has a small peak slightly above the voltage determined by the voltage division ratio, and if this peak voltage does not exceed the high level threshold of the input buffer Q1, the strobe signal is not changed until the external host device re-energizes. It is determined that the low level has been maintained.

FIG. 13 is a flowchart showing the operation of the conventional printer. First, when the power of the printer is turned on, the RAM 53, the interface 57, the panel unit 58, and the control circuit 54 are initialized in step S101, and the drive circuit 55 and the drive circuit 55 are driven via the control circuit 54 in the next step S102. The unit 56 is operated to perform an initial operation for initializing a printing position, printing conditions, and the like, and a printing standby state is set. When a print command is received from the external host device 50 in this state, the printing operation can be started.

Next, in step S103, it is determined whether or not the busy flag 73 is set, thereby detecting whether or not the level of the strobe signal has changed. Busy flag 73
Is set, and once set, the process proceeds to step S104 to start the timer TA and waits for a predetermined time to elapse in step S105. The standby time is set to 100 μm in consideration of a margin since the pulse width of the strobe signal is usually about several μsec.
Set to about seconds.

After a lapse of a predetermined time, the timer TA is stopped in step 106, and the level is determined by directly taking in the strobe signal via the general-purpose input / output circuit 74 in step S107. If the strobe signal has returned to the high level "H", it is determined that data has been input, and the received data latched by the data latch circuit 72 is read and stored in the print buffer of the RAM 53. Next step S
After clearing the busy flag 73 at 109, step S
At 110, it is determined whether or not the print start condition is satisfied, such as when the print buffer is full of data, and steps S103 to S110 are repeated until the print start condition is satisfied. When the print start condition is satisfied, the data in the print buffer is developed into a dot pattern in step S111, and the image forming unit 59 is driven to perform printing on the recording medium. Then, step S1
Return to 03.

On the other hand, in step S107, if the strobe signal remains at the low level "L" after a certain period of time has elapsed since the busy flag 73 is set, it is determined that the strobe signal is caused by powering off of the external host device 50. In step S112, the power saving signal 67 is set to low level to operate the power supply disconnecting circuit 62, and the power supply to the power supply line Vcc2 is stopped.

The normal printing operation and the power-off operation are switched by monitoring the voltage state of the strobe signal after a predetermined time has passed since the busy flag is set by the level inversion of the strobe signal.

[0023]

The conventional method is shown in FIG.
Although effective for the waveform shown in FIG.
A reliable determination cannot be made for the waveform shown in FIG. In the case of FIG. 12A, since the voltage of the strobe signal does not drop below the low-level threshold of the input buffer Q1, the busy flag is not set. As described above, since the strobe signal waveform when the power is turned off varies depending on the type of the external host device, a more reliable determination method is desired. For example, there is a possibility that a small peak in the waveform shown in FIG. 12B becomes slightly higher and exceeds the high level threshold value of the general-purpose input / output circuit 74, which may cause an erroneous determination.

An object of the present invention is to provide a printer capable of reliably determining the power state of an external host device.

[0025]

SUMMARY OF THE INVENTION The present invention provides an interface means for receiving a host-side signal output from an external host device, an image forming means for forming an image on a recording medium, and an interface means. And a main control unit for transmitting and receiving signals to and from the image forming unit and performing signal processing according to a predetermined program,
The first reference voltage set lower than the power supply voltage supplied to the interface means and the second reference voltage set higher than the low-level logic threshold and lower than the first reference voltage reduce the voltage of the host-side signal. Voltage monitoring means for monitoring, wherein the host-side signal is equal to or lower than the first reference voltage and
A printer device that determines that the power supply of an external host device is in a cut-off state when the voltage is equal to or higher than a reference voltage. Further, the invention is characterized in that the voltage monitoring means is an analog-to-digital converter. Further, the invention is characterized in that the voltage monitoring means is a window comparator. Further, according to the present invention, an interface unit for receiving a host-side signal output from an external host device, an image forming unit for forming an image on a recording medium, and the interface unit and the image forming unit In a printer device including a main control unit that transmits and receives a signal and performs signal processing according to a predetermined program, the printer device includes a voltage monitoring unit that monitors a voltage of a host-side signal, and a timer, and receives data from an external host device. After a predetermined time has elapsed after the absence of the host-side signal and the host-side signal has become equal to or lower than the first reference voltage set higher than the low-level logic threshold, the external host device A printer device that determines that a power supply is in an interrupted state. Further, the invention is characterized in that the voltage monitoring means is a comparator. Further, the invention is characterized in that the voltage monitoring means is an analog-to-digital converter. Further, the invention is characterized in that the first reference voltage can be automatically adjusted.

[0026]

According to the present invention, by monitoring the voltage of the host-side signal and comparing the voltage with the two reference voltages, it is possible to detect the intermediate potential other than the high level and the low level. Thus, when the host-side signal is equal to or lower than the first reference voltage and equal to or higher than the second reference voltage, it is possible to reliably and quickly determine that the power supply of the external host device is in the cutoff state. In addition to the strobe signal as the host-side signal, a signal that is sure to be at a high level or a low level when the external host device is in an energized state, and a signal that has an intermediate potential when the power supply is in a cut-off state are monitored. can do.

Also, by using an analog-to-digital converter as the voltage monitoring means, the signal processing in the main control means becomes easy, and the voltage change of the host-side signal can be monitored very finely.

Further, by using a window comparator as the voltage monitoring means, it is possible to accurately and quickly monitor the voltage change of the host-side signal.

According to the present invention, by monitoring the voltage of the host signal and comparing it with the first reference voltage set higher than the logical threshold value, it is possible to reliably detect the state where the host signal is at the intermediate potential. it can. Further, by judging the output of the voltage monitoring means after a lapse of a predetermined time from the level inversion of the host-side signal, whether the level inversion of the host-side signal is caused by data transfer or by a change in the power supply state of the external host device. Can be clearly determined.

Further, by using a comparator as the voltage monitoring means, it is possible to accurately and quickly monitor a change in the voltage of the host-side signal.

Further, by using an analog-to-digital converter as the voltage monitoring means, the signal processing in the main control means becomes easy, and the voltage change of the host side signal can be monitored very finely.

Further, since the first reference voltage can be automatically adjusted, it is possible to set a reference voltage that can be reliably determined when the impedance on the output side of the external host device greatly differs depending on the model.

[0033]

【Example】

(First Embodiment) FIG. 1 is a block diagram showing an electrical configuration of a first embodiment of the present invention. This printer device has a CPU (Central Processing Unit) 1 for managing the operation of the entire device, and a ROM (Read Only Memory) 2 which is a nonvolatile memory.
A data rewritable RAM (random access memory) 3, an interface (I / F) 7 for connecting to an external host device 19, signal input means such as operation switches, and a display LED (light emitting diode). It comprises a panel unit 8 in which signal display means such as a printer and a buzzer are incorporated, an image forming unit 9 for forming an image on a recording medium, a control circuit 4 for controlling the image forming unit 9, and the like.

The CPU 1 performs signal processing such as data input / output, data transfer, and operation in accordance with a program stored in the ROM 2. The ROM 2 stores programs and data necessary for the operation of the CPU 1, and data necessary for printing such as character codes and character fonts. RAM3 is CP
It is used for temporarily storing received data from the work area of U1 and the external host device and for expanding document data. The interface 7 exchanges data with the external host device 19. Further, the interface 7 is provided with a voltage monitoring circuit 15 for monitoring a level change of the strobe signal.

Such a CPU 1, ROM 2, RAM
3, the interface 7, the panel unit 8, and the control circuit 4 are mutually connected by a bus BUS including an address bus, a data bus, a control bus and the like. Also, C
A clock circuit (not shown) for generating a clock signal 16 for determining an operation timing is built in the PU 1, and is also supplied to the control circuit 4.

The image forming section 9 has a drive section 6 and a drive circuit 5. The drive unit 6 includes a print head that prints on a recording medium, a CR motor that moves a carriage (CR) on which the print head is mounted in the width direction of the recording medium, and a PF (paper feed) that conveys the recording medium by a fixed amount. It has a drive unit such as a motor. The drive circuit 5 includes the control circuit 4
The respective driving units of the image forming section 9 are driven based on the control signal from the CPU.

The printer includes a logic power supply 11 for supplying power to a logic circuit for handling digital signals.
And a drive power supply 10 for supplying electric power to a unit requiring relatively large electric power, such as a motor, are connected to a commercial power supply without a switch or the like. The drive power supply 10 supplies power to the image forming unit 9 via a power supply line Vcc3.

On the other hand, the logic power supply 11 is, for example, TTL
And a DC 5 V suitable for CMOS and CMOS is output to a power supply line Vcc1 and supplied to a power supply disconnection circuit 12 including a CPU 1, a ROM 2, a RAM 3, an interface 7, a panel unit 8, a control circuit 4, a relay, and the like. In addition, the power supply line V
A part of cc1 is supplied to the power supply line V via the power supply disconnection circuit 12.
cc2, which is connected to the panel unit 8 and a part of the control circuit 4. When the power saving signal 17 from the control circuit 4 is at a high level, the power supply disconnecting circuit 12
Power is supplied to c2, while when the power saving signal 17 is at low level, power supply to the power supply line Vcc2 is cut off.

FIG. 2 is a block diagram showing the interface 7 of the first embodiment. The external host device 19 and the interface 7 are connected via a connector 21. Here, a parallel interface system such as Centronics compliant is used, and data signals Data1 to 8 (positive logic) are used as representative signal lines. ), A busy signal BUSY (positive logic), a strobe signal STROBE (negative logic), an acknowledge signal ACK (negative logic), and the like.

The data latch circuit 22 outputs the data signal Da
The print code and the print control code transmitted from the external host device 19 via ta1 to ta8 are stored in units of 8 bits, and the data is latched when the strobe signal falls. The busy flag 23 is constituted by a flip-flop or the like, and becomes a high level at the falling of the strobe signal.
It is output as it is to the external host device 19 as a busy signal, and is taken into the CPU 1 via the general-purpose input / output circuit (I / O) 24. The external host device 19 constantly monitors the busy signal, and waits for the next data transmission until the signal becomes low. When the data latched by the data latch circuit 22 is taken into the CPU 1 via the bus, the CPU 1 outputs the clear signal CLEAR via the general-purpose input / output circuit 24 and inverts the busy flag 23 to a low level.

Further, in order to monitor the change in the voltage level of the strobe signal, there is provided a voltage monitoring circuit 15 including an AD converter (analog-to-digital converter) 15a having, for example, an 8-bit configuration.
Captured by U1. Note that a successive conversion type or the like can be used as the AD converter 15a.

FIG. 3 is a flowchart showing the operation of the first embodiment. First, when the power of the printer is turned on, initialization of the RAM 3, the interface 7, the panel unit 8, and the control circuit 4 is performed in step S201, and the drive circuit 5 and the drive circuit 5 are controlled via the control circuit 4 in the next step S202. The unit 6 is operated to perform an initial operation for initializing a printing position, a printing condition, and the like, and a printing standby state is set. When a print command is received from the external host device 19 in this state, a print operation can be started.

Next, in step S203, it is determined whether or not the busy flag 23 is set, thereby detecting whether or not the level of the strobe signal has changed. Busy flag 23
Is set, it is determined that there is data input,
In step S204, the received data latched by the data latch circuit 22 is read and stored in the print buffer of the RAM 3. Busy flag 2 in next step S205
After clearing No. 3, it is determined in step S206 whether or not the print start condition such as the print buffer being full of data is satisfied, and step S20 is performed until the print start condition is satisfied.
3 to S206 are repeated. When the print start condition is satisfied, the data in the print buffer is developed into a dot pattern in step S207, and the image forming unit 9 is driven to perform printing on the recording medium. Then, the process returns to step S203.

On the other hand, in step S203, the busy flag 2
If 3 does not stand, the process proceeds to step S208,
The operation of the AD converter 15a is started,
In step 09, the process waits until the AD conversion is completed. The time required for the AD conversion is determined by the number of bits of the conversion output and the clock frequency for the comparison operation.
The waiting time is about μ seconds.

Next, in step S210, the digital output of the AD converter 15a is compared with the first reference voltage V1.
The value of the first reference voltage V1 is stored in advance in the ROM 2 or the RAM 3, and in consideration of the case where the output impedance of the external host device 19 is relatively high, the closer the value of V1 is to 5V of the power supply voltage, the more the intermediate potential becomes. Although the detection margin becomes large, it is preferable to set the voltage to, for example, about 4 V of 80% in consideration of power supply voltage fluctuation and the like.

When the digital output of the AD converter 15a is higher than the first reference voltage V1, the external host device 19
Can be determined to be in the energized state, and the printer apparatus returns to step 203 to continue the print preparation state. If the digital output is equal to or less than the first reference voltage value V1, in step S211, the digital output is compared with the second reference voltage value V2. The value of the second reference voltage V2 is stored in advance in the ROM 2 or the RAM 3, and the detection margin of the intermediate potential becomes larger as the ground voltage becomes closer to 0V. It is preferable to set The digital output of the AD converter 15a is the second
When the voltage is lower than the reference voltage V2, it can be determined that the external host device 19 is in the energized state. When the digital output is equal to or higher than the second reference voltage V2, the voltage of the strobe signal is at an intermediate potential between the first reference voltage V1 and the second reference voltage V2.
It can be determined that the power of the external host device 19 has been cut off, the process proceeds to step S212, the power saving signal 17 is set to low level, the power supply disconnection circuit 12 is operated, and the power supply to the power supply line Vcc2 is stopped to save power. Enter power mode.

In the example shown in FIG. 12 (b), there is a possibility that the voltage after a sudden change in the signal may be measured. At this time, since the busy flag 23 is set, steps S203 to S206 are performed. After execution, step 208
The processing shifts to the subsequent A / D conversion processing, and steps S203 and S208 and thereafter are repeated until the voltage of the strobe signal is settled between the first reference voltage V1 and the second reference voltage V2.
When the potential reaches the intermediate potential, the process proceeds to step S212, and the printer enters a power saving mode.

When the power supply of the external host device 19 is on, the voltage of the strobe signal is usually equal to the first reference voltage V1.
Although described as higher, there is a case where the external host device 19 is transferring data exceptionally. When the strobe signal is low during data transfer, the first reference voltage V
1 or less, but since the determination of the busy flag 23 is performed prior to the A / D conversion processing, the steps S203 to S203 are performed.
In the normal data transfer, the next strobe signal is generated during this process and the busy flag 23 is set, so that there is no transition to the A / D conversion process during the data transfer. Although there is a possibility that the A / D conversion process may be started at an accidental timing, the strobe signal during data transfer does not reach the intermediate potential, and thus is excluded in step S210 or S211.

In this way, the voltage of the host-side signal is monitored,
When the voltage is equal to or lower than the first reference voltage V1 and equal to or higher than the second reference voltage V2, it is possible to reliably and quickly determine that the power supply of the external host device is in the cutoff state. Further, in this embodiment, since the determination is made in a routine different from the data reception routine, the speed of data reception is increased.

The above description shows a case where the power of the external host device 19 is turned on before the power of the printer device is turned on. Next, a case where the power of the printer device is turned on when the power of the external host device 19 is off will be described. In this case, the processes in steps S201 and S202 are performed in the same manner, and the busy flag 23 is determined in step S203. Here, since the external host device 19 is off, the busy flag 23 is not set. Thereafter, the process proceeds to step S208 and thereafter, the strobe signal becomes an intermediate voltage equal to or lower than the first reference voltage V1 and equal to or higher than the second reference voltage V2, and the printer power is turned off in step S212. Therefore, even if the power of the printer is turned on while the external host device is off, the printer is surely turned off after the predetermined processing is completed.

(Second Embodiment) FIG. 4 is a block diagram showing an interface 7 according to a second embodiment of the present invention. Note that the overall configuration of the printer device of the present embodiment is the same as that of the first embodiment, and will not be described repeatedly. Further, the interface 7 of this embodiment uses a window comparator composed of two comparators 15b and 15c as the voltage monitoring circuit 15, and the other configuration is the same as that of the first embodiment.

In order to monitor the change in the voltage level of the strobe signal, the comparator 15 compares the voltage with the first reference voltage V1.
b and a comparator 15c for comparing with the second reference voltage V2
Each output is an open collector type and is pulled up to a power supply line. The first reference voltage V1 and the second reference voltage V2 are supplied from a reference power supply (not shown), and are set to 4V and 1V, respectively, as in the first embodiment.

When the voltage of the strobe signal is 1) higher than the first reference voltage V1, the output of the comparator 15b goes low. 2) When the voltage of the strobe signal is lower than the first reference voltage V1 and higher than the second reference voltage, the comparator 15b. , 15c go to a high level, and 3) when it is lower than the second reference voltage V2, the output of the comparator 15c goes to a low level. Thus, a window comparator is formed, and its output is read into the CPU 1 via the general-purpose input / output circuit 24.

FIG. 5 is a flowchart showing the operation of the second embodiment. Here, steps S301 to S307
Are the same as S201 to S207 in the first embodiment, and a duplicate description will be omitted. If the busy flag 23 is not set in step S303 after the initialization processing after power-on, the process proceeds to step S308 to determine the output of the window comparator shown in FIG. When the voltage is equal to or higher than the reference voltage V1 or equal to or lower than the second reference voltage V2, it can be determined that the external host device 19 is in the energized state.

On the other hand, when the voltage of the strobe signal is lower than the first reference voltage V1 and higher than the second reference voltage, it can be determined that the power supply of the external host device 19 has been shut off, and the flow shifts to step S309 to shift to the power saving signal. 17 to a low level to operate the power supply disconnection circuit 12, and the power supply line Vcc2
To stop power supply and enter power saving mode.

The use of the window comparator as the power supply monitoring circuit 15 simplifies the program for the CPU 1 and eliminates the need for data conversion such as AD conversion, thereby speeding up the power supply monitoring routine.

(Third Embodiment) FIG. 6 is a block diagram showing an interface 7 according to a third embodiment of the present invention. Note that the overall configuration of the printer device of the present embodiment is the same as that of the first embodiment, and will not be described repeatedly. Further, the interface 7 of this embodiment uses one comparator 15b as the voltage monitoring circuit 15, and the other configuration is the same as that of the first embodiment.

In order to monitor the change in the voltage level of the strobe signal, the comparator 15 compares the voltage with the first reference voltage V1.
b is provided, the output of which is an open collector type and is pulled up to a power supply line. The first reference voltage V1 is
The voltage is supplied from a reference power supply (not shown), and is set to about 4 V as in the first embodiment.

When the voltage of the strobe signal is 1) higher than the first reference voltage V1, the output of the comparator 15b goes low, and 2) when the voltage of the strobe signal is lower than the first reference voltage V1, the output of the comparator 15b goes high. . The output is read into the CPU 1 via the general-purpose input / output circuit 24.

FIG. 7 is a flowchart showing the operation of the third embodiment. First, when the power of the printer is turned on, initialization of the RAM 3, the interface 7, the panel unit 8, and the control circuit 4 is performed in step S401, and the drive circuit 5 and the drive circuit 5 are driven via the control circuit 4 in the next step S402. The unit 6 is operated to perform an initial operation for initializing a printing position, a printing condition, and the like, and a printing standby state is set. When a print command is received from the external host device 19 in this state, a print operation can be started.

Next, in step S403, it is determined whether or not the busy flag 23 is set, thereby detecting whether or not the level of the strobe signal has changed. Busy flag 23
Is set, it is determined that data has been input, and the same processing as in steps S204 to S207 of the first embodiment is performed in steps S404 to S407. on the other hand,
If the busy flag 23 is not set in step S403, the output of the comparator 15b is fetched via the general-purpose input / output circuit 24 in step S408. If the voltage of the strobe signal is not lower than V1, step S403
To loop until the busy flag 23 is set. Here, if the voltage is lower than the first reference voltage V1,
In step S409, the timer TA is started, and in step S410, the process waits until a predetermined time has elapsed. The standby time is set to about 100 μsec with a margin, since the pulse width of the strobe signal is usually several μsec. After a lapse of a predetermined time, the timer TA is stopped in step S411, and the voltage is checked again in step S412. If the strobe signal is higher than the first reference voltage V1, there is a possibility that data has been input, and the process returns to step S403. However, if the voltage of the strobe signal is lower than V1 even after a certain period of time, it is determined that the strobe signal is caused by turning off the power of the external host device 19, and the flow shifts to step S413 to set the power saving signal 17 to low level and turn off the power. The cutting circuit 12 is operated to stop supplying power to the power supply line Vcc2.

While data transfer is not being performed,
The power of the host device 19 is monitored by comparing the voltage of the strobe signal with the first reference voltage V1 which is always set to be higher than the logical threshold value. Thus, the state where the host-side signal is at the intermediate potential can be reliably detected.

(Fourth Embodiment) The overall configuration of a printer according to the present embodiment is the same as that of the first embodiment, and will not be described repeatedly. Further, the interface 7 of the present embodiment is the first interface.
As in the embodiment, an A / D converter 15a is used as the voltage monitoring circuit 15. In this case, the temporal change of the strobe signal is monitored and compared with one reference voltage, and the reference voltage is automatically determined. Is adjusted.

FIG. 8 is a flowchart showing the operation of the fourth embodiment of the present invention. First, when the power of the printer is turned on, initialization of the RAM 3, the interface 7, the panel unit 8, and the control circuit 4 is performed in step S501, and the drive circuit 5 and the drive circuit 5 are driven via the control circuit 4 in the next step S502. The unit 6 is operated to perform an initial operation for initializing a printing position, a printing condition, and the like, and a printing standby state is set. In this state, the external host device 19
When the printing command is received from the printer, the printing operation can be started.

Next, in step S503, the operation of the AD converter 15a is started to measure the voltage of the strobe signal, and in step S504, the voltage is compared with the reference voltage V1 stored in the ROM 2 or the RAM 3 in advance. In the case of the embodiment, V1 is set to about 4V. If the measured value is larger than V1, the measured value is stored in the RAM 3 as the first reference voltage V1 in step S505.

In step S506, busy flag 2
3 to determine whether or not there is a change in the level of the strobe signal. If the busy flag 23 is set, it is determined that data has been input, and the first
As in steps S203 to S207 of the embodiment, step S50
In steps 6 to 510, data reading, clearing of the busy flag 23, presence / absence of a printing start condition, and printing processing are performed.

On the other hand, in step S506, the busy flag 2
If 3 does not stand, the process proceeds to step S511,
The A / D converter 15a is operated. Step S51
2, the measured value of the A / D converter 15a and the RAM
3 is compared with the first reference voltage V1. If the current measurement value is higher than the first reference voltage V1, the process returns to step S505 to update the first reference voltage V1.

If the current measurement value is equal to or lower than the first reference voltage V1, the process proceeds to step S513, where the difference between the current measurement value and the first reference voltage V1 is calculated, and an allowable reference value separately set in the RAM 3 is calculated. Compare with value Vm. The allowable reference value Vm is
Determined in consideration of the fluctuation of the power supply voltage, for example, 0.5 V
The degree is pre-selected. If the difference between the current measurement value and the first reference voltage V1 is equal to or less than the allowable reference value, the level of the strobe signal is stable, and the external host device 1
No. 9 determines that the power is on, and returns to step S505.

On the other hand, if the difference between the current measured value and the first reference voltage V1 is larger than the permissible reference value Vm, the strobe signal such as data transfer is changing every moment, and the process proceeds to step S514. Next, a timer is started, and a predetermined time is waited in step S515. The waiting time is selected to be about 100 μsec to determine the data transfer state.

Next, at step S516, the A / D converter 15a is operated again. At step S517, the measured value is compared with the first reference voltage V1 set in the RAM 3. If the measured value is equal to or greater than the value obtained by subtracting the allowable reference value Vm from the first reference voltage V1, the external host device 19 determines that the power is on, and returns to step S506.

On the other hand, if the measured value is smaller than the value obtained by subtracting the allowable reference value Vm from the first reference voltage V1, it can be determined that the power of the external host device 19 has been cut off, and the power-saving mode is entered in step S518. And exit.

In the above description, the case where the power of the external host device 19 is turned on before the power of the printer device is turned on is shown. Next, a case where the power of the printer device is turned on when the power of the external host device 19 is off will be described. In this case, the processes in steps S501 to S505 are performed in the same manner, and the busy flag 23 is determined in step S505. Here, since the external host device 19 is off, the busy flag 23 is not set. After that, the process proceeds to step S511 and thereafter.
At 518, the apparatus enters the power saving mode and ends. If the host is turned on before step S516, the process returns to step S506 by branching to step S517.
When AD conversion is performed in step S511, step S5
At 12, the measured value increases, and the process returns to step 505, where the measured value is stored as the first reference voltage V1. Thereafter, the same processing as when the external host device 19 is energized is performed.

By automatically adjusting the first reference voltage in this manner, a more reliable determination can be made.

As described above, in the fourth embodiment, the first reference voltage V
The method for automatically adjusting the first reference voltage V1 has been described. However, even when the first reference voltage V1 and the second reference voltage V2 are provided as shown in the first embodiment, the first reference voltage V1 is automatically adjusted in the same procedure. It is possible to

In the above embodiment, an example has been described in which a strobe signal is used as a host-side signal to be monitored. However, when the external host device is energized, it is a signal that is sure to be at a high level or a low level. Any signal that has an intermediate potential when in the power-off state can be used as a monitoring target.

[0076]

As described in detail above, according to the present invention, 2
By comparing using the two reference voltages, even when the voltage of the host-side signal is at an intermediate potential other than the high level and the low level, it is possible to detect the power supply state of the external host device reliably and at high speed. be able to.

Further, after a lapse of a predetermined time from the inversion of the level of the host signal, the voltage of the host signal is compared with the first reference voltage set higher than the logical threshold value, so that the power supply state of the external host device can be ensured. Can be determined quickly and quickly.

Further, by using the analog-to-digital converter as the voltage monitoring means, the signal processing in the main control means becomes easy, and the voltage change of the host side signal can be monitored very finely.

Further, by using a window comparator as the voltage monitoring means, it is possible to accurately and quickly monitor a voltage change of the host-side signal.

Further, since the first reference voltage can be automatically adjusted, a reliable determination can be made even if the type of the external host device changes.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a first embodiment of the present invention.

FIG. 2 is a block diagram showing an interface 7 of the first embodiment.

FIG. 3 is a flowchart showing the operation of the first embodiment.

FIG. 4 is a block diagram showing an interface 7 according to a second embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of the second embodiment.

FIG. 6 is a block diagram showing an interface 7 according to a third embodiment of the present invention.

FIG. 7 is a flowchart showing the operation of the third embodiment.

FIG. 8 is a flowchart showing the operation of the fourth embodiment of the present invention. First pudding

FIG. 9 is a block diagram illustrating an example of an electrical configuration of a conventional printer device.

FIG. 10 is a block diagram illustrating an example of an interface 57 of FIG. 9;

FIG. 11 is a circuit diagram illustrating an example of a connection method between an external host device and a printer device.

FIG. 12A is a graph illustrating an example of a voltage change of a strobe signal, and FIG. 12B is a graph illustrating another example of a voltage change of a strobe signal.

FIG. 13 is a flowchart showing the operation of a conventional printer device.

[Explanation of symbols]

 Reference Signs List 1 CPU 2 ROM 3 RAM 4 Control circuit 5 Drive circuit 6 Drive unit 7 Interface 8 Panel unit 9 Image forming unit 10 Drive power supply 11 Logic power supply 12 Power supply cutoff circuit 15 Voltage monitoring circuit 15a A / D converter 15b, 15c Comparator 16 clock Signal 17 Power saving signal 19 External host device 22 Data latch circuit 23 Busy flag 24 General-purpose input / output circuit

Claims (7)

(57) [Claims] An interface unit for receiving a host-side signal output from an external host device; an image forming unit for forming an image on a recording medium; and an interface unit and the image forming unit. A main control means for transmitting and receiving signals and performing signal processing in accordance with a predetermined program, wherein a first reference voltage set lower than a power supply voltage supplied to the interface means and a low-level logic threshold Voltage monitoring means for monitoring the voltage of the host-side signal with a second reference voltage that is set higher and lower than the first reference voltage, wherein the host-side signal is equal to or lower than the first reference voltage and equal to or higher than the second reference voltage In this case, the printer device determines that the power supply of the external host device is in a cut-off state. 2. The printer according to claim 1, wherein said voltage monitoring means is an analog-to-digital converter. 3. The printer according to claim 1, wherein said voltage monitoring means is a window comparator. 4. An interface unit for receiving a host-side signal output from an external host device, an image forming unit for forming an image on a recording medium, and the interface unit and the image forming unit. A printer device having main control means for transmitting and receiving signals and performing signal processing according to a predetermined program, comprising: a voltage monitoring means for monitoring a voltage of a host-side signal; and a timer, and a data input from an external host device is provided. After a predetermined time has elapsed after the absence of the host-side signal and the host-side signal has become equal to or lower than the first reference voltage set higher than the low-level logic threshold, the external host device A printer device that determines that a power supply is in a cut-off state. 5. The printer according to claim 4, wherein said voltage monitoring means is a comparator. 6. The printer device according to claim 4, wherein said voltage monitoring means is an analog-to-digital converter. 7. The printer according to claim 1, wherein the first reference voltage can be automatically adjusted.