JPH06149431A - Interface device - Google Patents

Abstract

PURPOSE:To enable data transfer reverse to the data transfer direction of a data line under the signal control of a control line, further, to simplify configuration and to improve economical efficiency. CONSTITUTION:After command processing is executed, transmitting data to a host computer 1 is prepared, and the state of a control line 5 is saved. In such a state, data transmission is requested to the host while turning a PError line to an 'H' level, turning an nFault line to an 'L' level and turning a Select line to the 'L' level. When a response from a host is confirmed by a control signal, data to be transmitted to the respective lines of a Busy line, PError line, nFault line and Select line are set from a bit '0' to a bit '3' and data transfer is performed while turning an nAck line to the 'L' level. After the existence of following data is continuously informed to the host, data to be transmitted to the respective lines of the Busy line, PError line, nFault line and Select line are set from a bit '4' to a bit '7' and data transfer is performed while turning the nAck line to the 'L' level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interface device for controlling transmission / reception of data and signals between a host computer and a printing device, for example.

[0002]

2. Description of the Related Art Centronics interface devices are widely used as parallel interfaces for controlling transmission and reception of data and signals between a host computer and a printing device. This interface device has a simple circuit configuration by a handshake in which the data transfer direction is unidirectional.

However, in recent years, printers having complicated mechanisms such as laser printers and color printers have become popular as printers,
In addition, the number of optional parts such as a paper feed tray and a paper discharge tray is also increasing, and the error information and maintenance information that the printing apparatus side has to notify the host computer side is increasing. On the other hand, in the Centronics interface device, the data transfer direction is one direction from the host computer to the printing device, and there is no choice but to use a control signal from the printing device side to the host computer side. It was not possible to give detailed information to the side.

As a means for solving this, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Laid-Open No. 4-76258, the data transfer direction of a data line for parallel transfer of data of a predetermined bit width can be switched, and at the time of switching the data transfer direction, the handshake line controls data transfer.
With this, it is known that detailed information can be notified from the printing device side to the host computer side.

[0005]

However, in the above-mentioned publication, the means for controlling the switching of the data transfer direction of the data line and the means for controlling the data transfer by the handshake line at the time of switching the data transfer direction of the data line are provided. There is a problem in that it becomes necessary and the structure becomes complicated and the cost becomes high.

Therefore, the present invention enables bidirectional transfer of data in a data line which has a plurality of control lines and a data line for parallel transfer of data of a predetermined bit width in one direction, and therefore can notify detailed information. Moreover, we are trying to provide an interface device that is simple in structure and excellent in economic efficiency.

[0007]

The present invention provides an interface device having a plurality of control lines and a data line for parallel transfer of data of a predetermined bit width, and the data transfer direction of the data line is unidirectional. Data transfer control means is provided for controlling the control lines and causing each of the control lines to function for data transfer in the direction opposite to the data transfer direction of the data line.

[0008]

In the present invention having such a structure, data lines are used to transfer data in one direction, and each control line is controlled to transfer data in the other direction. To do.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to interface control between a host computer and a printing apparatus.

In FIG. 1, 1 is a host computer, 2
Is a printing device. An interface device between the host computer 1 and the printing device 2, that is, parallel I / O
3 are connected by a data line 4 for parallel transfer of data of a predetermined bit width. The data line 4 has a unidirectional data transfer direction.
To transfer the print data to the parallel I / O 3 of the printing apparatus 2. Also, the host computer 1
And the parallel I / O 3 of the printer 2 are also connected by a plurality of control lines 5.

The parallel I / O 3 is of the Centronics specification, and the control line 5 includes an AutoFeed line, a SelectIn line, a Strobe line for transferring a signal from the host computer 1 to the printing device 2 and the printing device 2. It is composed of a Busy line for transferring a signal to the host computer 1, a PError line, an nFault line, a Select line and an nAck line.

The printing device 2 includes the parallel I / O 3
Besides, a CPU (central processing unit) that constitutes the main body of the control unit
6. ROM (read only memory) storing program data for the CPU 6 to control each part
7. A RAM (random memory) that stores a memory for storing the received print data or a memory for storing the data expanded into a dot pattern for actually printing the print data.
An access memory) 8, for example, a printing mechanism 9 including an electrophotographic process mechanism such as a laser oscillation unit, a photosensitive drum, a charging unit, a developing unit, a transfer unit, and a fixing unit is provided. Then, the CPU 6, the ROM 7, the RAM 8, and the parallel I / O 3
The printing mechanism 9 and the printing mechanism 9 are connected by a bus line 10.

The CPU 6 is programmed to perform the print control shown in FIG. That is, when the parallel I / O 3 receives data from the host computer 1, it is checked whether the received data is a command or print data. Then, if it is print data, the print data is expanded into a dot pattern and printing processing is performed.

If the received data is a command,
After executing the command processing, the host computer 1
Create send data to. And the current control line 5
Save the state of.

In this state, the host computer 1 is requested to transmit data. This request is made by the parallel I / O 3 setting the PError line to H (high) level, the nFault line to L (low) level and the Select line to L level, for example.

In this state, it waits for a response indicating that data is received from the host computer 1. This response is made by the host computer 1, for example, by setting the AutoFeed line to H level and the SelectIn line to L level.

AutoFeed line is at H level and SelectIn
When it is confirmed that the line has become L level, the control line 5 is controlled to transfer the data to the host computer 1. That is, bit 0 to bit 3 of the data to be transmitted are set to each of the Busy line, PError line, nFault line, and Select line, and the nAck line is set to L.
To level.

In this state, the host computer 1 waits for receiving data and setting the Strobe line to the L level. When the L level of the Strobe line is confirmed, when there is data to be transmitted subsequently, the nAck line is set to the H level. Then, set bits 4 to 7 of the data to be transmitted to the Busy line, PError line, nFault line, and Select line, and set the nAck line to L.
To level.

In this state, the host computer 1 waits for receiving data and setting the Strobe line to the L level. When the L level of the Strobe line is confirmed, when there is data to be transmitted subsequently, the nAck line is set to the H level and the Busy line, PError line, nFault line, Sele
Bits 0 to 3 of the next data are set in each line of the ct line and the same control is repeated.

When the data transmission is completed, Au is continued.
It waits until the toFeed line becomes L level and the SelectIn line becomes H level. That is, it waits until it is confirmed that the host computer 1 has recognized the completion of data transmission. And L level of AutoFeed line, SelectIn
When the H level state of the line is confirmed, the state of the control line that was initially saved is restored to the original state.

In the embodiment having such a configuration, the host computer 1 sets the Strobe line to the L level as shown in FIG. 3 (d) and sends a command to the data line 4 as shown in FIG. 3 (a). Forward. When the printer 2 receives the command, the Busy line is set to the H level to process the command as shown in FIG. 3 (f), and when the transmission data of the response to the command is created, the Busy line is set to the L level and the figure is displayed. As shown in (e) of 3, the nAck line is set to L level.

In this state, the state of the control line is saved, and the PError line is at the H level, the nFault line is at the L level, and the Select line is at the L level, as shown in (g), (h), and (i) of FIG.
The host computer 1 is requested to transfer data at the level.

In this state, as shown in (b) and (c) of FIG.
When it is confirmed that the AutoFeed line has become H level and the SelectIn line has become L level, the response from the host computer 1 is confirmed, and data transfer to the host computer 1 is started. That is, as shown in (f), (g), (h), and (i) of FIG. 3, Busy line, PError line, nFault line, Se
Set bits 0 to 3 of the data to be transmitted to each line of the lect line, and as shown in (e) of FIG.
Set the nAck line to L level.

Thus, bits 0 to 3 of the data are first transferred from the printer 2 to the host computer 1.

In this state, it waits until the Strobe line becomes L level, and the Strobe line becomes L level as shown in FIG. 3 (d).
When it reaches the level, it sets the nAck line to the H level to notify that data transfer will continue, then sets bits 4 to 7 of the data to be transmitted to the Busy line, PError line, nFault line, and Select line, And nA
Set the ck line to L level.

In this way, bits 4 to 7 of the data are transferred from the printer 2 to the host computer 1.

Then, the L level of the Strobe line, that is, the response from the host computer 1 is confirmed. When the data transmission is completed by this, the AutoFeed line is at the L level, Select
Wait for the In line to go to H level,
, (C) AutoFeed line is H level, Selec
When the tIn line goes into the L level state, the state of the control line that was initially saved is restored to the original state.

Since the data on the control line 5 can be controlled to transfer data from the printer 2 to the host computer 1 in this way, for example, the host computer 1 can print the data on the printer 2.
A command for inquiring the product identification number of the printing apparatus is provided in the command to the printer, and the printing apparatus 2 can transfer the product identification number data to the host computer 1 as data in response to this command. That is, the printing apparatus can notify the host computer of detailed information.

Moreover, since the data can be transferred from the printing device 2 to the host computer 1 only by controlling the signal on the control line 5 by software, the hardware does not require any change, and the configuration is simple and economical. It is excellent.

[0030]

As described above, according to the present invention, in a data line having a plurality of control lines and a data line for parallel transfer of data of a predetermined bit width in one direction, the data transfer direction of the data line is controlled by signal control of the control line. Data can be transferred in the opposite direction to that described above, and therefore detailed information can be notified, and the economy can be improved with a simple configuration.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing a printing process by the printing apparatus of the embodiment.

FIG. 3 is a diagram showing signal timings of a data line and a control line in the embodiment.

[Explanation of symbols]

 2 ... Printing device 3 ... Parallel I / O 4 ... Data line 5 ... Control line

Claims (1)

[Claims] 1. An interface device having a plurality of control lines and a data line for parallel transfer of data of a predetermined bit width, wherein the data transfer direction of the data line is unidirectional An interface device comprising data transfer control means for causing each control line to function for data transfer in a direction opposite to the data transfer direction of the data line.