JPH03192956A - Connecting method for communication line and picture formation device using the same - Google Patents

Abstract

PURPOSE:To reduce the number of the poles of a connector and the number of the lines of a signal cable without deteriorating the stability of a device by connecting a pair of control signals not to make two control means, at least, occupy a communication line at a time as overlapping by the same communication line. CONSTITUTION:A picture formation controller side is constituted of a NAND gate 1, a NOT gate 2, and a low pass filter consisting of a resistor 3 and a capacitor 4, and a sequence controller side too is constituted quite similarly of the NAND gate 5, the NOT gate 6, and the low pass filter consisting of the resistor 7 and the capacitor 8. Then, the output terminals of the picture formation controller side and the sequence controller side are connected by the signal cable 9. Namely, a pair of the control signals not to make two control means, at least, occupy the communication line at a time as overlapping are connected by the same communication line. Thus, the number of the poles of the connector and the number of the lines of the signal cable are reduced without deteriorating the stability of the device.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a communication line connection method, and particularly to a communication line connection method in an image forming apparatus such as a page printer, and an image forming apparatus to which this method is applied. .

[Prior Art] Conventionally, image forming devices such as page printers, especially laser beam printers, form bitmap image data based on data output from a host device such as a host computer or word processor, and communicate with the printer. (including the output of image data to the printer), and consists of an image forming controller that controls printing operations, and a sequence controller that controls all printing operations within the printer, such as electrophotographic processing, laser scanning, and paper transport. has been done.

The image forming controller and the sequence controller are connected through an interface as shown in FIG. Each signal of the conventional interface shown in FIG. 6 will be explained below.

In addition, the signals described as /- below are true (I2ow)
.

Defined as false (high).

/CPRDY is a signal indicating that serial communication is enabled with the sequence controller after the image forming controller is powered on; /PP
RDY is a signal indicating that serial communication with the image forming controller is possible after the sequence controller is powered on; /CPRDY
Serial communication is possible when both of and /PPRDY are true (βow).

In this serial communication, the image forming controller sends command data to the sequence controller, and in response, the sequence controller sends status data corresponding to the received command data to the image forming controller. /RDY is a signal indicating that preparation for a printing operation within the printer is completed and printing is possible, and is output from the sequence controller to the image forming controller. /PRNT is a signal indicating that the image forming controller has completed forming the image data to be printed and instructs the sequence controller to start printing.

/TOP is a synchronization signal in the paper transport direction, that is, a vertical synchronization signal, and /BD is a horizontal synchronization signal indicating the start of scanning of the laser beam in the horizontal direction. /TOP and /
For BD, the data is output from the sequence controller to the image forming controller. /VDO is an image signal to be printed by the printer, and is output from the image forming controller to the sequence controller.

FIG. 7 shows the timing at which /TOP, /BD, and /VDO are output. After /T is output from the sequence controller, /BD is output for each line. The image forming controller serially sends image data to the image printing area pixel by pixel to the sequence controller in synchronization with this /BD.

Next, in FIG. 6, /SC and /SCL are /CBS
Y, /5BSY is a signal line for serial communication performed between the image forming controller and the sequence controller. /SC is a transmission line for serial information, that is, command data and status data; command data is sent from the image forming controller, and status data is sent from the sequence controller.

/SCL is a serial clock synchronized with /SC, and is output from the image forming controller when communicating command data, and from the image forming controller or sequence controller when communicating status data. /CBS
Y is a signal indicating that the image forming controller occupies the /SC line in order to send command data to the sequence controller, and /5BSY is a signal indicating that the sequence controller occupies the /SC line in order to send status data to the image forming controller. This is a signal indicating that the space is occupied.

FIG. 8 shows the timing of serial communication.

FIG. 9 is an example of a circuit on the sequence controller side of the serial communication line. Since /SC and /SCL are bidirectional signals, an oven collector (O
, C, ) output NAND gate is connected to the signal input side (SC-
IN2 and LK-IN2 side) a low-pass filter determined by the R+Ct constant and a Schmitt trigger type NO
A T gate is used. /CBSY becomes the input and is connected to a low-pass filter (time constant R2C2) and Schmitt trigger type N
In the OT gate, /5BSY is the output, which is composed of NAND of oven collector (O, C,) outputs. On the other hand, the circuit on the image forming controller side is /SC and /5
CLK has exactly the same configuration, /CBSY and /5BSY are respectively /5BSY and /5BSY on the sequence controller side.
It has a configuration equivalent to CBSY.

[Problems to be Solved by the Invention] However, in the above conventional example, as shown in FIG. 8, the command data and /CBSY sent from the image forming controller, and the status data and /5BSY sent from the sequence controller Having two separate signal lines for /CBSY and /5BSY increases the number of signal line cables and the number of connector pins, which increases the area occupied by the connector. There was a problem of high cost.

Furthermore, as shown in Figure 9, in the conventional circuit example, each signal line is made into a twisted pair (a configuration in which a signal line and a RET line are paired) to eliminate the influence of reflection, but all signal lines are made into twisted pairs. The increase in the number of pins in connectors and the number of wires in signal cables caused by this change led to a significant increase in costs.

The present invention eliminates the above-mentioned conventional drawbacks and provides a signal line connection method that reduces the number of connector poles and the number of signal cable lines without reducing the stability of the device.

Further, a compact and inexpensive image forming apparatus to which the above connection method is applied is provided.

[Means for Solving the Problem] In order to solve this problem, the communication line connection method of the present invention is a communication line connection method that connects at least two different control means within one device, comprising: A set of control signals that do not simultaneously monopolize a communication line by the at least two control means are connected through the same communication line.

Further, a pair of one signal line and the other signal line that maintains a ground level while the one signal line is sending a pulse train is a twisted pair.

The image processing device of the present invention also performs image formation in which bitmap image data is formed based on print data output from a host computer, etc., and command data is sent to a printing device via communication to control printing. and a sequence control means for controlling the printing operation of a printing device having an electrophotographic processing unit, a laser scanning system, a paper conveyance system, etc., and transmitting status data to the image forming means in response to received command data. An image forming apparatus comprising: transmitting a signal to a predetermined communication line to instruct the image forming means to transmit command data during the command data transmission period; a first communication control means that receives a signal from the communication line instructing that status data be transmitted, and instructs the sequence control side that the command data is transmitted during the command data transmission period; A second communication control means is provided which receives a signal from the communication line and sends a signal to the communication line instructing that the status data is transmitted during the status data transmission period.

Here, between the image forming means and the sequence control means, one signal line that outputs a pulse train and the other signal line that does not output a pulse train during the output period of the pulse train of the signal line are connected. combine.

[Operation] In such a configuration, a predetermined set of signal lines is reduced to one signal line, and one signal does not output a pulse train while the other signal outputs a pulse train, or the signal level of the other signal is not in a transition state. By combining them in pairs, interference with other signals is reduced, and the number of signal cable lines and the number of connector pins are minimized to reduce costs.

[Example] Hereinafter, the present invention will be explained according to illustrated embodiments.

FIG. 1 is a circuit diagram showing an embodiment in which the present invention is applied to a signal line between an image forming controller and a sequence controller of an image forming apparatus.

In the figure, the image forming controller side includes an open collector type NAND gate 1 and a Schmitt trigger type NAND gate 1.
OT gate 2, resistor 3 and capacitor 4 (time constant is RC
) and a low-pass filter.

On the other hand, the sequence controller side is also composed of an oven collector type NAND gate 5, a Schmitt trigger type NOT gate 6, and a low-pass filter including a resistor 7 and a capacitor 8 in exactly the same manner.

Here, it is assumed that the output ends of the image forming controller side and the sequence controller side are connected by a signal cable 9.

5CBSY-OUTI from image forming controller is NA
When output to the input terminal of ND gate l, /5 is output to the output terminal.
CBSY is output and NO on the sequence controller side
Input of T gate 6 and NO on image forming controller side
5CBSY-I which is the input of T gate 2 and is the output
N2 and 5CBSY-INI and are input to the image forming controller and sequence controller.

On the other hand, 5CBSY-OUT from the sequence controller
2 is output, 5CBS is output from the output terminal of NOT gate 2 on the image forming controller side and from the output terminal of NOT gate 6 on the sequence controller side in exactly the same way.
Y-INI and 5CBSY-IN2 will be input.

FIG. 2 shows the timing of the /5CBSY signal shown in FIG. 1 together with other serial communication signals /SC and /SCL. As shown in the figure, the command data and status data are composed of 8 bits.
Transmit on the /SC line in synchronization with SCL.

In the case of command data communication, the image forming controller sets /5CBSY to false (high), that is, 5CBSY-
Confirm that the INI is false (42ow) and enter /5C
True BSY (42ow) i.e. 5CBSY-00T
After setting I to true (high), set the command data to /SC
Synchronize with L and send it out on the /SC line, and set /5CBSY to false (high) after the transmission is finished. On the other hand, the sequence controller makes /5CBSY true (βOW), that is, 5CBSY-IN2 goes true (high). After confirming that the command has been set, enter command data on the /SC line in synchronization with /SCL.

In the case of status data communication, after confirming that /5CBSY is false (high), the sequence controller sets /5CBSY to true (βOW) and synchronizes the status data with /SCL. Send on the line, and after the sending is finished, /5CBSY is set to false
h), whereas the image forming controller
Confirm that /5CBSY has become true (f2ow) and receive status data on the /SC line in synchronization with /5CLK.

In the circuit configuration shown in FIG. 1, the image forming controller is
By setting 5CBSY-OUTI to true (high) during command data communication, /5CBSY at the output terminal of NAND gate 1 becomes true (βOW), and
5CBSY-INI from the output terminal of NOT gate 2 also becomes true (high), but in this case, the image forming controller itself sets 5CBSY-OtlTl to true (high) before sending out the command data, so 5CBSY-
By ignoring IN2, it is possible to prohibit command data input from /SC shown in FIG. 9 from being input as status data.

FIG. 3 is a schematic flowchart of the operating procedure of this embodiment.

First, in step Sll, a command is transmitted from the image forming controller side.

The sequence controller side waits for reception of a command in step S21, and if received, executes the command in step S22, and then transmits the current status in step S23.

On the other hand, after sending the command in step SLl, the image forming controller waits for the status from the sequence controller side in step S12, determines whether this status is the status to which the next command should be sent, and if so, sends a new command in step S13. send a command. In this way, step 524-S25→S26 and step S1
Controls the operations from step 4 onwards.

Here, the procedure for transmitting a command from the image forming controller side in step Sll or step S13 will be explained as follows.
As shown in the flowchart of Figure A, first, in step S31, it is determined whether 5CBSY-INI is high or βOW, and β
If OW, this signal line is not used, so in step S32, set 5CBY-00TI to high/5CBSY to n.
Let it be ov. In step S33, a command is transmitted via the /SC signal line. After sending, set 5CBY-0υTl to I
Set the power to 20W/5CBSY to high.

Similarly, the procedure for transmitting the status from the sequence controller side in step S23 or step S26 is shown in the flowchart of FIG. 4B. This processing procedure is the fourth
5CBSY-INI and 5CBY-OUTI in figure A
This is a replacement for CBSY-IN2 and 5CBY-OUT2, and detailed explanation will be omitted.

FIG. 5 is a diagram showing a second embodiment in which the present invention is applied to a signal line between an image forming controller and a sequence controller of an image forming apparatus.

In this example, a combination of signal lines forming a twisted pair in a signal cable connecting an image forming controller and a sequence controller is shown. The number of pins of the connector connected to the signal cable is 15, and each signal is divided into print status and serial signal system, image data and image control signal system, and power signal system, and each signal is arranged.
Each signal system has one ground line.

In the same figure, in the combination of /PRNT and /RDY,
/RDY from the sequence controller is true (βOW
), from the image forming controller /PRN
The T pulse is not output, and the signal level transitions of /PRNT and /RDY do not occur simultaneously and there is no interference, so a twisted pair is used. Also, /SC and /5CBS
Similarly, for group Y, when communicating command data, the image forming controller sets /5CBSY to true (βOW), then the command data is sent on /SC, and after the sending is completed, /5
When CBSY is set to false (high) and status data is communicated, the sequence controller sets /5CBSY to true (
After the status data is set to βow), the status data is sent on /SC, and after the sending is completed, /5CBSY is set to false (high), so in this case as well, the signal level transitions of /SC and /5CBSY do not occur at the same time. A twisted pair is used because there is no interference.

Although this embodiment has been explained using a communication line between an image forming controller and a sequence controller in an image processing apparatus, the communication line connection method of this example can also be applied to other apparatuses that are desired to be simplified and made more compact. That is clear.

[Effects of the Invention] According to the present invention, it is possible to provide a signal line connection method that reduces the number of connector poles and the number of signal cable lines without reducing the stability of the device.

Furthermore, it is possible to provide a compact and inexpensive image forming apparatus to which the above connection method is applied.

Specifically, when the present invention is applied to an image forming apparatus, communication between an image forming controller and a sequence controller is performed using a conventional serial communication method in which command data and serial data communication is controlled using /CBSY and /5BSY. , to create /5CBSY, and by outputting a pulse train, paying attention to the output state of each signal that communicates, by making the two signals into a twisted pair, the interference with other signal lines is reduced, Costs are also reduced by minimizing the number of signal cable wires and connector pins.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of /5CBSY which is the first embodiment of the present invention, Fig. 2 is a timing diagram of serial communication, Fig. 3 is a flowchart showing an outline of the operating procedure of the first embodiment, and Fig. 4A is FIG. 4B is a flowchart showing the procedure for transmitting a command, FIG. 5 is a diagram showing the arrangement of each signal on the signal cable according to the second embodiment of the present invention, and FIG. 6 is a diagram showing the arrangement of signals in the conventional example. FIG. 7 is a timing chart of image signals and image control signals; FIG. 8 is a timing chart of conventional serial communication; and FIG. 9 is a circuit diagram of conventional serial communication signals. In the figure, 1.5...NAND gate, 2.6...NO
T gate, 3.7...Resistor, 4.8...Capacitor, 9...Signal cable.

Claims (4)

[Claims] (1) A method for connecting a communication line between at least two different control means in one device, wherein a set of control signals is provided that does not allow the at least two control means to monopolize the communication line at the same time. A communication line connection method characterized in that the communication lines are connected by the same communication line. (2) Claim 1 further characterized in that the pair of one signal line and the other signal line that maintains a ground level while the one signal line is transmitting a pulse train is a twisted pair.
How to connect the communication line described in section. (3) An image forming means that forms bitmap image data based on print data output from a host computer, etc., and sends command data to a printing device via communication to control printing, and an electrophotographic process. an image forming apparatus comprising: a sequence control means for controlling a printing operation of a printing device having a section, a laser scanning system, a paper conveyance system, etc., and sending status data to the image forming means in response to received command data; A signal instructing the image forming means to transmit command data during the command data transmission period is sent to a predetermined communication line, and status data is transmitted during the status data transmission period. a first communication control means that receives a signal from the communication line instructing that the command data be transmitted during the command data transmission period to the sequence control side; An image forming apparatus comprising: second communication control means for receiving and sending to the communication line a signal instructing that the status data be transmitted during the status data transmission period. (4) Between the image forming means and the sequence control means, one signal line that outputs a pulse train and the other signal line that does not output a pulse train during the output period of the pulse train of the signal line. The image forming apparatus according to claim 3, characterized in that the image forming apparatus is used in combination.