JP2002052779A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate matching of timing between an acknowledge signal and a busy signal by controlling the timing of the acknowledge signal and busy signal by firmware. SOLUTION: The printer 1 comprises an interface with a personal computer 2, i.e., a Centronix interface connector 11, a logical circuit IC dedicated for the printer, i.e., an ASIC 12, and a CPU 13 for controlling the ASIC 12. Signal lines L1, L2,..., Ln for connecting the ASIC 12 with the Centronix interface connector 11 are connected, respectively, with capacitors C1, C2,..., Cn for blocking radiation of radio wave. The ASIC 12 is controlled by software such that the timing of a busy signal and an acknowledge signal being outputted to the personal computer 2 is limited within a regulated value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus which is connected to an external device via a Centronics interface connector, and has at least a signal line for outputting an acknowledgment signal inserted with a capacitor for preventing radio wave radiation. More particularly, the present invention relates to a printing apparatus that controls a busy signal so that the timing between a busy signal and an acknowledge signal standardized as IEEE1284 is kept within a standard value.

[0002]

2. Description of the Related Art Centronics interface connectors used for connecting a printer as a printing device to a personal computer as an external device include IEEE.
Various signal waveform standards are defined in 1284. In particular, regarding the relationship between the busy signal and the acknowledge signal, 500 ns from the rise of the acknowledge signal
It is defined as a standard to change the busy signal within ec.

[0003] Such a Centronics interface connector is described in, for example, Japanese Utility Model Application Laid-Open No. 62-1.
There are those described in JP-A-92450 and JP-A-10-39968. Japanese Unexamined Utility Model Publication No. 62-192450 relates to an interface converter in which a printer having a normal Centronics interface can be connected to a personal computer having a simple Centronics interface.
Japanese Unexamined Patent Publication No. 68-68138 relates to an interface device which has improved responsiveness of a change in signal level on a receiving side to a change in signal level on a transmitting side.

By the way, apart from such a standard value, generally, in electronic equipment, electromagnetic interference (EMI: electromagnetic interference) in which noise such as electromagnetic waves is output to the outside by radiation or conduction.
EMC (electromagnetic compatibil) that prevents noise from being output to the outside, including measures against ticinterference
)) needs to be taken.

[0005] Therefore, in order to prevent such radiation of noise (as a measure against EMC), in a printer having a Centronics interface connector, the Centronics interface connector is connected to an ASIC which is a logic circuit IC dedicated to the printer. A capacitor for preventing radiation of radio waves is inserted in each signal line between them. That is, a capacitor for preventing radio wave radiation is also inserted into a signal line for outputting an acknowledge signal from the printer to the personal computer. This allows
For example, the waveform as shown in FIG. 4A is blunted as shown in FIG. 4B to prevent noise radiation.

On the other hand, if EMC measures are taken by inserting a capacitor in this way, the waveform becomes rounded,
It becomes difficult to comply with the standard of the busy signal and the acknowledgment signal based on the above-mentioned IEEE1284, that is, the standard of changing the busy signal within 500 nsec from the rise of the acknowledge signal.

For example, a 1000 pF capacitor was inserted to take EMC countermeasures. However, this was not sufficient, and a 2000 pF capacitor was inserted. As a result, the rise of the acknowledge signal was further reduced, and For example, the rise and the change of the busy signal may be reversed, for example, and the standard may not be complied with. For this reason, the capacitance of the capacitor must be returned to 1000 pF, and the EMC countermeasures remain insufficient. Therefore, it is necessary to take EMC countermeasures in a place different from the capacitor. Usually, C
Adjustments are made with the PU clock or a ferrite core is inserted to take measures against noise at the source oscillation. Also, if the measures against such source oscillation are not enough, add a bead core at the interface part,
We take measures such as inserting chip beads.

[0008]

As described above, in the conventional printer, the EMC countermeasure by inserting a capacitor and the observance of the standard of the busy signal and the acknowledge signal based on IEEE1284 conflict with each other.
There is a problem that there is a limit in EMC measures by inserting a capacitor.

In addition, since the generation of the acknowledge signal or the busy signal is performed by the ASIC, if the standard cannot be complied with, the ASIC needs to be replaced, but the replacement takes about three months. Therefore, there was also a problem that it was not possible to easily replace it.

The present invention has been made to solve such a problem, and its object is to provide a firmware.
By controlling the timing of the acknowledgment signal and the busy signal, the timing of the acknowledgment signal and the busy signal can be easily adjusted.
An object of the present invention is to provide a printing apparatus capable of sufficiently performing EMC measures by inserting a capacitor without replacing an ASIC.

[0011]

In order to solve the above-mentioned problems, a printing apparatus according to the present invention is connected to an external device via a Centronics interface connector and emits at least a signal line for outputting an acknowledge signal. In a printing apparatus in which a blocking capacitor is inserted, software control is performed so that the output timing of the busy signal output to the external device and the acknowledgment signal is kept within a standard value.

According to the present invention having the above features,
Since the output timing of the busy signal and acknowledge signal is controlled by software so as to keep it within the standard value,
Even if the standard value is not considered, EMC measures can be sufficiently taken by freely setting the capacitance of the capacitor.
In addition, since noise can be sufficiently removed by EMC measures by inserting a capacitor, noise measures by source oscillation and noise measures by the interface section are not required.
EMC measures are easier.

Further, in the printing apparatus according to the present invention, in the above-described configuration, the software control is performed by delaying a timing of switching a level of the busy signal.
It is characterized in that the time from when the acknowledge signal rises to the “H” level to when the level of the busy signal is switched is controlled to be within a standard value. Further, in the printing apparatus of the present invention, in the above configuration, the timing of switching the level of the busy signal is determined by a rising waveform of the acknowledgment signal corresponding to a capacity of a capacitor inserted in a signal line of the acknowledgment signal. Is determined in consideration of only

As described above, since the timing for switching the level of the busy signal can be controlled by software control, a very flexible system can be constructed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration diagram of a printing system including the printing apparatus of the present invention. This printing system is a system in which a printer 1 as a printing device performs a printing operation based on print data supplied from, for example, a personal computer 2 as an external device. Therefore, the personal computer 2 and the printer 1 are connected via a communication cable 3 capable of bidirectional communication.

The printer 1 includes a Centronics interface connector 11 as an interface with the personal computer 2, an ASIC 12 as a logic circuit IC dedicated to the printer, and a CPU 13 for controlling the same. Has a key sensor 1 for detecting key operations such as a power key and a paper key.
4 are derived. The ASIC 12 also includes a feed motor 15 for feeding a recording sheet to a printing position, a carrier motor 16 for reciprocating a carrier on which a print head 17 is mounted in a direction orthogonal to the recording sheet feed direction, A print head 17 for printing data by ejecting ink on the recording paper thus formed is connected. ASI
The feed motor 15, the carrier motor 16 and the print head 1 are controlled by the CPU 13.
7 is controlled. The signal lines L1, L2,..., Ln connecting the ASIC 12 and the Centronics interface connector 11 have capacitors C1, C2,.
n are connected.

In the printing system having such a configuration,
At the time of printing operation, when the strobe signal and the data signal are transmitted from the personal computer 2, the ASIC 12 of the printer 1 outputs an acknowledge signal, which is a response signal indicating that the data signal has been received, to the personal computer 2 in response to the strobe signal. Send to 2. Further, the printer 1 transmits a busy signal to the personal computer 2 when the print data is fully stored in the internal memory (not shown). And
As described above, the relationship between the busy signal and the acknowledge signal is defined in detail in IEEE 1284, and as shown in FIG. 2A, the acknowledge signal (nA
It is defined as a standard that the busy signal (Busy) is changed within 500 nsec from the rise of the clock signal (ck).

On the other hand, in the present embodiment, the capacitor C
EMC measures are taken by setting the capacity of 1, C2,..., Cn to an optimum value. In other words, conventionally,
Due to the relationship with the IEEE 1284 standard, only a capacitor with a capacitance of up to about 1000 pF could be inserted. However, in this embodiment, since the timing between the acknowledge signal and the busy signal can be controlled by software, for example, 2
It is also possible to insert a capacitor having a capacitance of 000 pF or 3000 pF. That is, it is possible to completely implement the EMC countermeasure only by the capacitance of the capacitor.

In this case, the capacitors C1, C2,.
Since the EMC countermeasure is performed by using Cn, the waveform of the acknowledgment signal becomes a blunt waveform from the rising time (time t1) as shown in FIG.
3 will substantially rise. That is,
In this example, the rise of the acknowledge signal (time t)
3) and the change of the busy signal (change from “H” level to “L” level: time t2) are reversed. The time T1 (t3-t2) is also the standard 500 ns.
ec has been exceeded.

Therefore, in the present embodiment, as shown in FIG. 2C, the change of the busy signal, that is, the timing of changing from the "H" level to the "L" level, is controlled by the ASIC 12 at time T2. The time T3 is set to be time t4, and the time T3 from time t3 at which it is determined that the acknowledge signal has risen to time t4 is 500 ns of the standard.
ec.

Thus, while complying with the standard of the busy signal and the acknowledge signal by IEEE1284,
The measure C can be sufficiently performed only by the inserted capacitor.

FIG. 3 shows another embodiment of the timing control of the acknowledge signal and the busy signal. In this example, as shown in FIG. 7A, the relationship between the timing of the rise of the acknowledge signal and the timing of the rise of the busy signal (change from “L” to “H”) is shown. That is, the busy signal is changed from “L” level to “H” level within 500 nsec from the rise of the acknowledge signal.

In this case, the capacitors C1, C2,.
Since the EMC countermeasure is performed by using Cn, the waveform of the acknowledge signal becomes a blunt waveform from the rising time (time t11) as shown in FIG. 3B, and substantially rises at time t13. Become. That is, in this example, the rise of the acknowledge signal (time t13) and the change of the busy signal (from “L” level to “H”)
Change to level: time t12) is reversed. The time T11 (t13-t12) also exceeds the standard of 500 nsec.

Therefore, in this example, as shown in FIG. 3C, the change of this busy signal, that is, the timing of changing from the "L" level to the "H" level under the control of the ASIC 12, is time T12. Delayed to time t14,
Time t1 at which it is determined that the acknowledge signal has risen
The time T13 from 3 to time t14 is defined as 500n of the standard.
It is set to be within sec.

Thus, while complying with the standard of the busy signal and the acknowledge signal according to IEEE1284, the EM
The C countermeasure can be sufficiently taken only by the inserted capacitor.

That is, the timing check of each signal waveform of Centronics greatly changes depending on the condition of a PCB (printed wiring board) or ASIC just before mass production, so that there are many restrictions in EMC countermeasures. By controlling the timing in a software manner (firmware manner), the timing of each signal waveform can be easily adjusted, and EMC measures can be sufficiently dealt with only by the capacitance of the capacitor.

[0027]

According to the present invention, there is provided a printing apparatus which is connected to an external device via a Centronics interface connector and has at least a signal line for outputting an acknowledgment signal inserted with a capacitor for preventing radio wave radiation. In addition, the output timing of the busy signal and the acknowledgment signal output to the external device is controlled by software so as to be within the standard value. That is, since the output timing of the busy signal and the acknowledge signal is controlled by software so as to be within the standard value, the EMC measures can be taken sufficiently by freely setting the capacitance of the capacitor without worrying about the standard value. Can be done. In addition, since noise can be sufficiently removed by EMC measures by inserting a capacitor, noise measures by source oscillation and noise measures by an interface section are not required, and EMC measures are simpler.

According to the printing apparatus of the present invention, the software control is to delay the timing of switching the level of the busy signal so that the acknowledge signal is raised to the “H” level and then the level of the busy signal is reduced. It is configured to control so that the time until switching is kept within the standard value. Further, the timing of switching the level of the busy signal is determined in accordance with the capacity of the capacitor inserted into the signal line of the acknowledgment signal, considering the rising waveform of the acknowledgment signal. As described above, the timing at which the level of the busy signal is switched can be controlled by software control, so that a PCB (printed wiring board) or ASIC just before mass production can be used.
Irrespective of the situation described above, the timing of each signal waveform can be easily adjusted, and EMC measures can be sufficiently dealt with only by the capacitance of the capacitor.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a printing system including a printing device of the present invention.

FIG. 2 is a waveform diagram showing an embodiment of timing control of an acknowledge signal and a busy signal.

FIG. 3 is a waveform diagram showing another embodiment of timing control of an acknowledge signal and a busy signal.

FIG. 4 is an explanatory diagram showing signal waveforms before and after an EMC measure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Printer 2 Personal computer 3 Communication cable 11 Centronics interface connector 12 ASIC 13 CPU 14 Key sensor 15 Feed motor 16 Carrier motor 17 Print head L1, L2, ..., Ln Signal line C1, C2, ..., Cn Capacitor to block radiation

Claims (3)

[Claims] 1. A printing device which is connected to an external device via a Centronics interface connector and has a capacitor for preventing radiation of radio waves inserted at least in a signal line for outputting an acknowledge signal. A printing apparatus wherein software-controlled so that output timings of an output busy signal and the acknowledge signal are kept within a standard value. 2. The software-based control delays the timing of switching the level of the busy signal so that the time from when the acknowledge signal rises to “H” level to when the level of the busy signal is switched is set. 2. The printing apparatus according to claim 1, wherein the printing apparatus is controlled so as to be within a standard value. 3. The timing of switching the level of the busy signal is determined in accordance with the capacity of a capacitor inserted into the signal line of the acknowledgment signal, taking into account the blunt rising waveform of the acknowledgment signal. The printing device according to claim 2, wherein: