JP2983115B2 - Interface device - Google Patents

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 and reception of data and signals between a host computer and a printing apparatus.

[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 apparatus. This interface device is a handshake in which the data transfer direction is unidirectional, and has a simple circuit configuration.

In recent years, however, printing apparatuses having complicated mechanisms such as laser printers and color printers have become widespread.
Also, the number of optional components such as a paper feed tray and a paper discharge tray has increased, and information on errors and maintenance that must be notified from the printing apparatus to the host computer has increased. On the other hand, in the interface device of the Centronics specification, the data transfer direction is one direction from the host computer to the printing device, and a control signal must be used from the printing device side to the host computer side. Could not give detailed information to the side.

As a solution to this problem, see, for example,
As disclosed in Japanese Patent Application Laid-Open No. 4-76258, it is possible to switch the data transfer direction of a data line for transferring data of a predetermined bit width in parallel, and to control data transfer by a handshake line when switching the data transfer direction.
It is known that the printing apparatus can notify the host computer of detailed information.

[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 transfer of data by the handshake line when switching the data transfer direction of the data line are disclosed. However, there is a problem that the configuration becomes complicated and the cost increases.

Therefore, the present invention enables bidirectional transfer of data in a device having a plurality of control lines and a data line for transferring data of a predetermined bit width in one direction in parallel, and thus can provide detailed information notification. In addition, we aim to provide an interface device that is simple and economical.

[0007]

According to the present invention, there is provided an interface device having a plurality of control lines and a data line for transferring data of a predetermined bit width in parallel, wherein the data transfer direction of the data line is unidirectional. It controls the control line, of the respective control line, the data transfer direction of the data line for transmitting a control signal in the opposite direction
Set the control line in the opposite direction to the data transfer direction of the data line.
And data transfer control means for functioning for data transfer in the opposite direction and for controlling the data transfer.

[0008]

According to the present invention having such a configuration, data transfer is performed in one direction using data lines, and each control line is controlled to transfer data in the other direction using each control line. Do.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a description will be given of a case where 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, a parallel I / O
3 are connected by a data line 4 for transferring data of a predetermined bit width in parallel. The data line 4 is a line in which the data transfer direction is unidirectional, and the host computer 1
To transfer the print data to the parallel I / O 3 of the printing apparatus 2. The host computer 1
And the parallel I / O 3 of the printing apparatus 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 is an AutoFeed line, a SelectIn line, a Strobe line for transferring a signal from the host computer 1 to the printing device 2, and a control line 5 from the printing device 2. It comprises a Busy line, a PError line, an nFault line, a Select line, and an nAck line for transferring a signal to the host computer 1.

The printing device 2 includes the parallel I / O 3
CPU (Central Processing Unit) that constitutes the control unit body
6. ROM (read only memory) storing program data for the CPU 6 to control each part
7. A random access memory (RAM) having a memory for storing received print data and a memory for storing data developed 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. The CPU 6, the ROM 7, the RAM 8, the parallel I / O 3
And the printing mechanism 9 via a bus line 10.

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

If the received data is a command,
After executing the command processing, the host computer 1
Create data to send 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 to the effect that data is received from the host computer 1. This response is made by the host computer 1 setting the AutoFeed line to H level and the SelectIn line to L level, for example.

When the 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 data to the host computer 1. That is, bits 0 to 3 of the data to be transmitted are set to 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 to receive data and set the Strobe line to L level. When the L level of the Strobe line is confirmed, if there is data to be transmitted subsequently, the nAck line is set to the H level. Then, bits 4 to 7 of the data to be transmitted are set to 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 to receive data and set the Strobe line to L level. When the L level of the Strobe line is confirmed, if there is data to be transmitted further subsequently, the nAck line is set to the H level, and the Busy line, PError line, nFault line, Sele
The same control is repeated by setting bits 0 to 3 of the next data in each line of the ct line.

When data transmission is completed, Au
It waits until the toFeed line is at the L level and the SelectIn line is at the H level. That is, the process waits until the host computer 1 confirms that the data transmission has been completed. And L level of AutoFeed line, SelectIn
When the H level state of the line is confirmed, the state of the control line that has been saved first is returned 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. 3D and sends a command to the data line 4 as shown in FIG. 3A. Forward. When the printing apparatus 2 receives the command, it sets the Busy line to the H level as shown in FIG. 3 (f) to process the command. The nAck line is set to the L level as shown in FIG.

In this state, the state of the control line is saved, and as shown in (g), (h) and (i) of FIG. 3, 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.
A request is made to the host computer 1 for data transfer at the level.

In this state, as shown in FIGS. 3 (b) and 3 (c),
When it is confirmed that the AutoFeed line is at the H level and the SelectIn line is at the 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, the Busy line, PError line, nFault line,
The bit 0 to bit 3 of the data to be transmitted to each line of the lect line are set, and as shown in FIG.
Set the nAck line to L level.

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

In this state, the system waits until the Strobe line goes low, and as shown in FIG. 3D, the Strobe line goes low.
When the level reaches the level, the nAck line is set to the H level to notify that the data transfer will be continued, and then bits 4 to 7 of the data to be transmitted to the Busy line, PError line, nFault line, and Select line are set. And nA
The ck line is set to L level.

Thus, the bits 4 to 7 of the data are transferred from the printing apparatus 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 with this, the AutoFeed line becomes L level,
Waits for the In line to go to the H level state, and FIG.
As shown in (c), the AutoFeed line is at the H level,
When the tIn line goes to the L level state, the state of the control line that was first saved is returned to the original state.

As described above, data can be transferred from the printing apparatus 2 to the host computer 1 by controlling the signal on the control line 5.
A command for inquiring the product identification number of the printing apparatus is provided as a command to the printer, and in response to this command, the printing apparatus 2 can transfer the product identification number data to the host computer 1 as data. That is, detailed information can be notified from the printing apparatus to the host computer.

In addition, since the data can be transferred from the printing apparatus 2 to the host computer 1 only by controlling the signal on the control line 5 by software, no change is required as hardware, and the configuration is simple and economical. It is excellent. The printing device uses the nAck line to send data
Since the transfer length is controlled, the printing device is the main
Can send detailed information via the control line.
Transfer data between the host computer 1 and the printing device 2.
There is no need to make an agreement on the length of

[0030]

As described above, according to the present invention, in a device having a plurality of control lines and a data line for transferring data of a predetermined bit width in parallel in one direction, each control line has
Of which, control in the direction opposite to the data transfer direction of the data line
Data transfer and control using a control line to send signals
Control of data transfer, and therefore via data lines
The data receiving side is mainly responsible for
Thus, detailed information can be notified, and economical efficiency can be improved with a simple configuration.

[Brief description of the drawings]

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

FIG. 2 is a flowchart illustrating a printing process performed by the printing apparatus according to the embodiment.

FIG. 3 is a view showing signal timings of data lines and control lines in the embodiment.

[Explanation of symbols]

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

Claims (1)

(57) [Claims] 1. A data a plurality of control lines with a predetermined bit width and a data line for parallel transfer, the interface device data transfer direction of the data line is unidirectional, the control result together with the respective control line
, Out of their respective control line, the data transfer direction of the data lines transmits a control signal to the reverse control line
An interface device provided with data transfer control means for functioning as data transfer in a direction opposite to the data transfer direction of the data line and for controlling the data transfer.