JPH10105511A - Centronics interface controller - Google Patents

Abstract

(57) Abstract: The present invention relates to a Centronics interface control device, and more particularly, to a Centronics interface control device capable of preventing data corruption and performing high-speed print processing. SOLUTION: An MPU 2 sets set data in a PLD 6 in advance, and reads collation data input through a Centronics interface 8 into the MPU 2 through a buffer 7 at a timing according to the set data set in the PLD 6, For example, collation with collation data stored in the ROM 3 is performed. If both collation data match by this processing, the shorter set data is set in the PLD 6, the above processing is repeated, and the set data is reduced to the limit where data can be transmitted normally, and the shortest strobe signal (STROBE1) Is set so that print data can be captured. By setting in this way, it is possible to provide a Centronics interface control device that transmits print data at high speed without causing a transmission error and is not affected by noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Centronics interface control device for connecting a host device such as a personal computer to a printer.

[0002]

2. Description of the Related Art A printer connected to a host device such as a personal computer performs a printing process based on print information output from the host device. For this reason, a host device such as a personal computer and a printer are connected by a parallel or serial interface. Particularly, a Centronics interface having a parallel configuration is widely used as a standard for connecting a computer and a printer.

When data is exchanged between a computer (upper device) and a printer using the Centronics interface controller, the following control is performed. First, a strobe signal is output from the computer side and, for example, 1-byte print data is output to the printer device. The printer processes input print data, outputs a busy signal to the computer during the data processing period, and outputs an acknowledgment signal when the input processing of 1-byte print data is completed. When the acknowledgment signal is input, the computer determines that the next print data can be transmitted, and outputs the next one-byte print data in synchronization with the strobe signal. Hereinafter, print data is transferred from the computer to the printer by repeating the same processing.

[0004]

As described above, a strobe signal is a signal output from a host device to a printer. The printer processes a busy signal while processing print data input in synchronization with the strobe signal. And outputs an acknowledge signal upon completion of processing. Therefore, a computer (host device) having a slow processing speed requires time to output print data (strobe signal), and cannot perform high-speed printing.

[0005] On the other hand, a cable (Centronics interface specification) for connecting a host device and a printer is also provided.
The configuration may be long depending on the installation location restrictions and system settings. For example, the cable length may be 5 m to 10 m. When the length of the cable is increased as described above, problems such as overshoot, undershoot, and reflection occur, which causes so-called data corruption.

When the cable length increases, the amount of noise picked up between them also increases. For example, if noise with a short pulse width of about 30 ns to 100 ns enters the strobe signal,
The printer device determines that data has been input from a higher-level device, and responds to the data, causing garbled characters.

[0007] In order to solve the above-mentioned problems, the present invention provides a Centronics interface control device capable of preventing data corruption and performing high-speed print processing.

[0008]

According to the first aspect of the present invention, in order to solve the above problems, a response signal is output based on a strobe signal output from a higher-level device, and a response signal is output to the higher-level device in synchronization with these signals. A centronics interface control device for transmitting and receiving data, wherein the output timing variable control means variably controls the timing of outputting the response signal based on the reception of the strobe signal, and a signal output variable by the output timing variable control means. Centronics for transmitting and receiving data by setting, in said output timing variable control means, the fastest timing condition capable of maintaining normal transmission by said transmission state identification means. This can be achieved by providing an interface controller.

The output timing variable control means sets a data transmission state in which, after capturing data output from the host device in synchronization with the strobe signal, a character signal is not generated and a response signal can be output in the shortest time. Therefore, the setting time of the strobe signal is set to the shortest,
The transmission state identification means identifies the transmission state in which the response signal is output in the shortest time without causing garbled characters while the output timing variable control means changes the output timing of the strobe signal, and sets the condition to the output timing. Set the variable control means.

With this configuration, data transmission is performed in accordance with the optimum transmission state set in the output timing variable control means, and print data output from a higher-level device is fetched at a limit where normal reception is possible. It performs high-speed transmission.

According to a second aspect of the present invention, the response signal is, for example, a busy signal indicating that data output from a higher-level device is being processed. It is.

According to the above configuration, since the strobe signal is set in the shortest time, the output of the busy signal is also stopped quickly, and the next print data can be taken in from the host device at high speed.

According to a third aspect of the present invention, the response signal is, for example, an acknowledgment indicating that the processing of data output from the higher-level device has been completed. Signal.

With the above configuration, since the strobe signal is set in the shortest time, the output of the acknowledgment signal is similarly output quickly, and the next print data can be fetched from the host device at high speed.

According to a fourth aspect of the present invention, the invention described in the first aspect is further embodied, and the data output from the host device is, for example, print information. The print information includes, for example, character codes and various commands, and is used for printing processing in the printer device.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a system block diagram of the Centronics interface control device of the present embodiment. In FIG. 1, a Centronics interface control device 1 is provided in a printer device, and includes an MPU (microprocessor unit) 2 as transmission state identification means, a ROM 3, a RAM 4, and an output timing variable section (hereinafter referred to as output timing variable control means). GA) 5, a pseudo strobe signal output unit (hereinafter referred to as PLD) 6, a buffer 7, and a Centronics interface 8. The MPU 2 controls the Centronics interface control device of the present embodiment based on a program stored in the ROM 4 and also controls printing of a printer device (not shown). The ROM 3 also stores collation data described later. The RAM 4 is composed of a reception buffer and a work area. The print data supplied from the host device is input to the reception buffer, and various data generated during the processing operation of the MPU 4 is written to the work area.

The GA 5 is a circuit for outputting a busy signal or an acknowledge signal to a host device in accordance with the control of the MPU 2, and the set data output from the MPU 2 is
A set signal (CS) for setting to D6 is output to PLD6. When print data output from the host device is supplied to the MPU 2, the print data is supplied to the MPU 2 via the GA 5.

The PLD 6 has the above-mentioned set signal (CS).
, The set data is input from the MPU 2 and a clock signal (CLK) is input from a circuit (not shown). Also, P
The strobe signal (S
TROBE) is input and the strobe signal (STRO)
BE) is input, the clock signal (CLK) is counted. When the input of the clock signal (CLK) reaches the value of the set data, the pseudo strobe signal (STROB) is input.
E1) is output. This pseudo strobe signal (STRO)
BE1) is output to the MPU 2 and the buffer 7. The pseudo strobe signal (STROBE1) controls the output timing of a busy signal and an acknowledge signal described later.

The buffer 7 receives collation data from the Centronics interface 8, and receives data from the PLD 6.
, A pseudo strobe signal is input. The buffer 7 holds the input collation data, and outputs the collation data to the GA 5 when the pseudo strobe signal (STROBE1) is input. That is, the buffer 7 receives the pseudo strobe signal (STROBE1) after the collation data is actually input.
This is a circuit for holding the collation data until is output.
It should be noted that the data output from the higher-level device is, of course, print data during normal printing. In this example, however, in order to set the pseudo strobe signal (STROBE1), the higher-level device outputs 1-byte collation data.

The Centronics interface 8 is connected to a host device (not shown) via a cable, and outputs collation data output from the host device to the buffer 7. Also, the strobe signal (STRO) output from the host device
BE) to the above-mentioned GA5 and PLD6. Conversely, it outputs a busy signal and an acknowledge signal output from the GA 5 to the host device.

Next, the control operation of the Centronics interface control device having the above configuration will be described. FIG. 2 shows operation timings in the case of a normal control operation. That is, the strobe signal (ST
ROBE) is input, a busy signal is output, and the output of the busy signal is stopped at time t1 after the output of the strobe signal (STROBE) is stopped. The acknowledgment signal is the strobe signal (ST
ROBE) is output a predetermined time after the output is stopped,
Thereafter, the output is stopped after a certain time has elapsed. still,
The certain time during which the acknowledgment signal is output is a time sufficient for notifying the host device that the print data reception processing on the printer device has been completed.

FIG. 3 is a flow chart for explaining the processing operation of the Centronics interface control device of the present embodiment. Hereinafter, the operation will be described with reference to the flowchart of FIG. First, when the power of the apparatus is turned on (step (hereinafter referred to as S
1), the MPU 2 executes an initial setting process,
The reset processing of each circuit such as M4, GA5 and PLD6 is performed, and "12" which is the initial set data (X) is set in PLD6 (S2). The set data "12" is set as follows. That is, P
The cycle of the clock signal (CLK) input to the LD 6 is, for example, 40 ns, and the output time of the strobe signal is 0.5.
Assuming μs, the number that can be sampled by the clock signal (CLK) is 12.5. Therefore, while the strobe signal is being output, the number (integer value) that can be sampled by the clock signal (CLK) is “12”,
For this reason, the set data "12" is output to the PLD 6, and is set in the PLD 6 as an initial value of the set data (X).

Further, the MPU 2 sets an initial value (Y) in a predetermined area of the RAM 4 at the time of the initial setting processing (S
3). Note that the initial value (Y) is a configuration in which the same operation is repeated a plurality of times (for example, three times) to obtain the reliability of data, and thus the initial value (Y) is set to the initial value (Y) first. Set to “1”. As described above, after performing the initial setting process of the Centronics interface control device of the present example, the strobe signal (STRO) output from the higher-level device is performed.
Wait for input of BE). The following description includes the time chart of FIG.

A strobe signal (STROB) is sent from a host device.
When E) is input, the PLD 6 counts the clock signal (CLK) subsequently input to the PLD 6. And PL
When the number of clocks of the clock signal (CLK) input to D6 reaches the set data “12”, a pseudo strobe signal (STROBE1) is output to the buffer 7 (S
4 is YES). Here, the above set data "12" is almost the same as the output duration of the strobe signal (STROBE), and this pseudo strobe signal (STROBE)
After the output of 1), the output of the busy signal is stopped after the time t1, and the next data is supplied from the host device by the output of the acknowledge signal. That is, the collation data held in the buffer 7 by the output of the pseudo strobe signal (STROBE1) is input to the MPU 2 via the GA 5, and is written to the specified address of the RAM 4. This is because the time t1 is sufficient. The output of each signal at this time is at the timing shown in FIG.

In this example, the data supplied from the host device at this time is not the print data but the collation data as described above, and is the collation data for confirming the data transmission error. That is, the collation data is a 1-byte collation data. For example, the collation data “1” is transmitted from the host device to the MPU 2 and collated with the collation data “1” stored in the ROM 3 in advance. If the above-mentioned collation result is correct, the MPU 2 determines that one byte has been normally received (YES in S5), and the next determination (S5).
Go to 6). This determination (S5) is for determining whether or not the set data (X) is "3". Since the current set data is "12" as described above, the determination (S6)
Is NO.

Next, the MPU 2 decrements the set data by -1 (S7), and sets the set data "11" to the PLD 6
Set to. Thereafter, the collation data is transmitted from the host device to the MPU 2 as described above, and collated with the collation data stored in the ROM 3 in advance. At this time, 1
The byte collation data is, for example, “2” and the ROM 3
It is determined that one byte has been successfully received when the data matches the collation data stored in (5) (YES in S5). The output of each signal at this time is at the timing (b) shown in FIG. Therefore, at this time, the pseudo strobe signal (STROBE)
Since the output time of 1) is shorter than the strobe signal by 40 ns, the timing of stopping the output of the busy signal is also shortened by the same time, and the pseudo strobe signal (STRO)
The processing time of print data output in synchronization with BE1) can also be reduced.

Next, the MPU 2 executes the above judgment (S6) and processing (S7), and stores the next collation data "3" in the ROM.
It is determined whether or not the collation data stored in No. 3 matches, and if they match (YES in S5), it is determined that no error has occurred in data transmission. The output of each signal at this time is shown in FIG.
The timing shown in FIG. Therefore, at this time, the output time of the pseudo strobe signal (STROBE1) is shorter than the strobe signal (STROBE) by 2 × 40 ns, so that the output stop timing of the busy signal can be shortened, and the output is synchronized with the strobe signal (STROBE). The processing time of the print data to be processed can be reduced by 80 ns.

Hereinafter, by repeating the above determination and processing, the collation data output from the higher-level device is “4”,
Are sequentially updated as “5”,... And the set data is “3”
Repeat until. If no error occurs in the collation data until the set data becomes "3", when a strobe signal is input, a transmission error also occurs due to the output of the short pseudo-strobe signal (STROBE1) of (5) shown in FIG. It is determined that the print data can be transmitted without the print data. Therefore, in this case, the transmission time can be reduced by the time t2 every time one byte of collation data is transmitted, and the total printing time can be reduced.

On the other hand, if any of the set data is garbled during the above processing (S5 is N)
O), the MPU 2 determines whether the set data at that time is “12” (S8). That is, in this case, the collation data "1" at the time of the set data "12" and the collation data stored in the ROM 3 do not match. At this time, the MPU 2 determines that an abnormal error has occurred, and displays, for example, an alarm (S9). . The set data "12" is a pseudo strobe signal (STROBE1) which is almost the same as the normal strobe signal (STROBE) shown in FIG. 2 described above. Perform error display.

On the other hand, when 1-byte data cannot be received normally when the set data is other than "12" (S5 is N)
O, S8: NO), +1 is added to the set data X at that time (S10), and it is determined again whether 1-byte data cannot be normally received (S11, S12). For example, if the set data in which the mismatch has occurred is “9”, the same processing is performed after resetting the set data to “10” in the PLD 6.
In this case, the process is performed before for the set data “10”, and the collation data should normally match without any problem (YES in S12). Therefore, if the collation data matches at this time, the set time of the pseudo strobe signal which can transmit the print data to the printer without causing a transmission error is 2 × 4 times the output time of the reference strobe signal.
It is determined that the time is obtained by subtracting 0 ns.

Next, the MPU 2 increments the initial value Y written in the RAM 4 by +1 (S13), and judges whether this Y value has reached "3" (S14). As described above, this Y value is obtained by repeating the above-described determination and processing (S11 to S13) three times. By performing the same processing three times and confirming a transmission error, a malfunction due to noise or the like is avoided. For example, in the above example, after the set data is incremented by +1 and reset to “10”, if an error does not occur in two more verification processes (that is, if the verification data matches), the set data is changed to “10”. It is determined that the print data can be processed without error using the corresponding pseudo strobe signal that is 80 ns shorter.

If the collation data does not match in the above process, the set data is incremented by +1 again (S10), and set data is set so that three collation processes can be performed without errors such as garbled characters.

The set data set as described above is registered in the GA 5 under the control of the MPU 2. For example, when the set data is the above “10”, the data “1”
"0" is registered in GA5. Therefore, thereafter, a busy signal and an acknowledge signal are output in accordance with the data set as described above, and the print data output from the host device is written into the RAM 4. In addition, the pseudo strobe signal used at this time is shorter than the original strobe signal by the time t2, and the output of the acknowledge signal can be shortened by the corresponding time, so that the transmission speed of the print data can be increased.

On the other hand, the Centronics interface control device of the present embodiment, in addition to the above-described high-speed processing of print data,
It also has a function of removing noise that enters the strobe signal (STROBE).

FIG. 5 is a diagram for explaining this. In other words, even when noise having a short pulse width as shown in the figure appears in the strobe signal (STROBE), the centronics interface control device of the present embodiment outputs the busy signal and the acknowledge signal at the output timing of the strobe signal (STROBE) itself. It does not output.
In this example, a busy signal and an acknowledge signal are output in accordance with a pseudo strobe signal (STROBE1). As shown in FIG.
There is no noise on E1). That is, the pseudo strobe signal (STROBE1) is a signal generated in synchronization with the clock signal (CLK), and is a signal without noise. Therefore, the Centronics interface control device of this example also has a function as a noise filter.

In this embodiment, the busy signal and the acknowledge signal have been described as confirmation signals, but other confirmation signals can be applied regardless of the name. Further, the collation data is not limited to data such as “1” and “2”, and the data amount does not necessarily have to be one byte.
For example, collation data of several bits may be used,
Alternatively, collation data having a configuration of several bytes may be used.

[0037]

As described above, according to the present invention, a confirmation signal such as a busy signal or an acknowledge signal is output at a limit timing at which print data can be transmitted normally, so that the print data transmission speed can be increased. As a result, the print processing speed is improved.

Further, even when noise is present in the strobe signal, the strobe signal is not affected by the noise, so that accurate print data transmission processing can be performed.

[Brief description of the drawings]

FIG. 1 is a system block diagram of a Centronics interface control device according to an embodiment of the present invention.

FIG. 2 is a time chart showing operation timing in the case of a normal control operation.

FIG. 3 is a flowchart illustrating a processing operation of the Centronics interface control device of the embodiment.

4A is a time chart for set data “12”, FIG. 4B is a time chart for set data “11”, and FIG. 4C is a time chart for set data “10”. FIG. 9D is a time chart when set data is “9”, and FIG. 9E is a time chart when set data is “5”.

FIG. 5 is a diagram for explaining that the Centronics interface control device of the present embodiment has a noise removing function.

[Explanation of symbols]

 1 Centronics interface controller 2 MPU 3 ROM 4 RAM 5 GA 6 PLD 7 Buffer 8 Centronics interface

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[Procedure amendment]

[Submission date] December 5, 1996

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

Claims (4)

[Claims] 1. A Centronics interface control device that outputs response signals based on strobe signals output from a host device and transmits and receives data to and from the host device in synchronization with these signals. Output timing variable control means for variably controlling the timing of outputting the response signal on the basis of reception; and transmission status identification means for identifying a data transmission status at a signal output timing varied by the output timing variable control means. A centronics interface control device, wherein a maximum speed timing condition under which normal transmission can be maintained by the transmission state identification means is set in the output timing variable control means, and data is exchanged. 2. The Centronics interface control device according to claim 1, wherein the response signal is a busy signal indicating that data output from the host device is being processed. 3. The Centronics interface control device according to claim 1, wherein the response signal is an acknowledgment signal indicating that the processing of the data output from the host device has been completed. 4. The data output from the higher-level device is:
4. The Centronics interface control device according to claim 1, wherein the control information is print information.