JPH04307834A - Parallel/serial conversion transmission circuit - Google Patents

Abstract

PURPOSE:To surely send a parallel data signal comprising data synchronized with a strobe signal and an asynchronous data through one transmission line. CONSTITUTION:A transmission section 1 is provided with a strobe monitor timer 12, which monitors a strobe signal occurrence interval at all times and the section 1 sends periodically data asynchronized with the strobe signal even when the strobe signal is not generated for a long period. Even when a strobe signal is generated while a parallel serial conversion circuit 13 makes conversion processing, the data is surely sent by latching a parallel data to a latch circuit 11. When the strobe signal is not generated for a long period, it is required to send only the data asynchronized with the strobe signal and in order to distinguish this case from the case of sending all data, a control bit is provided in a transmission packet. The control bit is decided by a data output circuit 23 in a reception section 2 and only a required data is outputted. Thus, the data is surely sent through one transmission line.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] Converts parallel data, which is a mixture of data synchronized to strobe signals and data asynchronous to strobe signals, as typified by parallel printer interfaces, into serial data and transmits it to the receiving side. The present invention relates to a parallel/serial conversion/transmission circuit that transmits data by converting it back into parallel data.

0002

[Prior Art] When converting parallel data, in which data synchronized to a strobe signal and data asynchronous to a strobe signal are mixed, to serial data and transmitting the data, in the conventional technology, as shown in FIG. Using transmission lines, data synchronized with the strobe signal and data asynchronous to the strobe signal were transmitted using separate transmission lines. In this method, data synchronized with the strobe signal is sampled at the timing of the strobe signal generation, converted from parallel to serial, and then output to the transmission line, converted from serial to parallel on the receiving side, and output. The strobe signal is regenerated by the strobe generation circuit,
Output. On the other hand, data asynchronous to the strobe signal is sampled at a preset sampling period, subjected to parallel-to-serial conversion, and then output to a transmission line, and then serial-to-parallel converted and output on the receiving side.

[0003] In this way, in the conventional method, by using two transmission lines, two types of data with different characteristics, synchronous data and asynchronous data, can be transmitted completely independently with respect to the strobe signal. was completed.

0004

[Problems to be Solved by the Invention] However, in order to realize transmission using the conventional technology, two transmission lines were required. The present invention provides a parallel-to-serial conversion transmission circuit that converts parallel data, in which data synchronized with a strobe signal and data asynchronous to a strobe signal are mixed, into serial data and transmits the data using only one transmission line. This is what we provide.

[0005]

[Means for Solving the Problems] A parallel/serial conversion/transmission circuit of the present invention converts parallel data consisting of data synchronized with a strobe signal and asynchronous data into serial data and transmits the serial data. , a strobe monitoring timer that monitors the generation interval of the strobe signal and outputs a signal instructing the latch circuit to latch if the strobe signal is not generated for a predetermined time; Latch and set control bit to 1
and a latch circuit that latches only data asynchronous to the strobe and outputs the control bit as 0 when a latch instruction is output from the strobe monitoring timer, and a latch circuit that outputs the control bit as 0 from this latch circuit. a parallel-serial conversion circuit that converts parallel data into parallel-serial data and outputs a serial data signal; a serial-parallel conversion circuit that inputs the serial data signal output from the parallel-serial conversion circuit and converts it into parallel data;
When the control signal in the parallel data output from the serial-parallel conversion circuit is 1, all parallel data and the strobe signal are output, and when the control signal in the parallel data is 0, only data asynchronous to the strobe signal is output. It is characterized by comprising an output circuit that outputs an output.

[0006]

[Operation] When a strobe signal is input, the latch circuit of the transmitter latches all parallel data and passes the data to the parallel-to-serial conversion circuit. The parallel-to-serial conversion circuit performs parallel-to-serial conversion on this data and outputs it to the transmission line. However, this alone causes a problem that if the strobe signal is not generated for a long time, data asynchronous to the strobe signal will not be transmitted during this period. Therefore, the strobe monitoring timer constantly monitors the generation interval of strobe signals, and if no strobe signal is generated for a certain period of time, outputs a signal instructing latch to the latch circuit, which receives this signal and Latch only data asynchronous to the strobe signal. The latched parallel data is converted by the parallel-to-serial conversion circuit, but if a strobe signal is generated while the parallel-to-serial conversion circuit is converting the latched data according to instructions from the strobe monitoring timer. , the parallel data signal cannot be immediately input to the parallel-to-serial conversion circuit. However, since the latch circuit operates due to the generation of the strobe signal,
The parallel data signal is latched, and after the conversion process of the parallel/serial conversion circuit is completed, the latched data can be converted from parallel to serial. In this way, the latch circuit functions as a buffer for parallel data signals.

[0007] The data output from the latch circuit to the parallel-to-serial converter circuit is provided with one bit corresponding to the strobe signal, and when the latch circuit is latched by the strobe signal, this bit is The bit is set to 1, and this bit is set to 0 if the operation was performed based on an instruction from the strobe monitoring timer. The bit corresponding to this strobe signal will be referred to as a control bit. The control bit, together with other data latched by the latch circuit, is converted from parallel to serial and output to the transmission line.

The structure of the packet output from the parallel-to-serial conversion circuit is the same regardless of whether a strobe signal is generated, but the nature of the packet can be distinguished depending on the state of the bit corresponding to this strobe signal. Can be done. In other words, if the control bit is 0, data synchronized with the strobe signal in the transmission packet is meaningless and invalid data, and only data asynchronous with the strobe signal is valid, but the control bit If the bit is 1, all data in the transmitted packet is valid.

[0009] The serial data output to the transmission line is input to a serial-to-parallel conversion circuit of the receiving section and is converted into parallel data. This parallel data is output to the outside by a data output circuit. At this time, if the control bit is 0, only data asynchronous to the strobe signal is output. Also, the control bit is 1
If so, all data is output, and the strobe signal is reproduced and output in the strobe generation circuit.

As described above, by using only one transmission line, both data synchronous with the strobe signal and data asynchronous with the strobe signal can be reliably transmitted.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing an embodiment of a parallel/serial conversion/transmission circuit according to the present invention.

Note that the parallel data signals shown in this embodiment include a strobe signal STR and this strobe signal ST.
Signals DA1, DA2 and strobe signal S synchronized with R
It is assumed that TR consists of 5-bit data of asynchronous signals DB1 and DB2.

The parallel/serial conversion/transmission circuit shown in the figure converts a parallel data signal containing a mixture of data synchronized with a strobe signal and data asynchronous to the strobe signal into a serial data signal in a transmitter 1. Data transmission is performed by sending the signal to the receiving section 2 through a main transmission line 3 and converting it again into a parallel data signal at the receiving section 2. Examples of the sending side and the receiving side include, for example, a personal computer and a printer.

The transmitter 1 converts the input parallel data signal into a serial data signal and outputs it.
This includes a latch circuit 11, a strobe monitoring timer 12, and a parallel/serial conversion circuit 13.

In the latch circuit 11, when the strobe signal is input, all data DA1, DA2, DB1, DB2
is latched, the control bit is set to 1, and the data is passed along with these data to the parallel/serial conversion circuit 13.

The strobe monitoring timer 12 monitors the generation interval of the strobe signal, and outputs a signal instructing the latch circuit to latch if the strobe signal is not generated even once within a preset time. This timer is reset when a strobe signal is generated and when a signal instructing the latch circuit to latch is output.
Start again.

The latch circuit 11 performs latching not only when the strobe signal described above is generated but also when receiving a latch instruction from the strobe monitoring timer 12. However, the data to be latched at this time is only data DB1 and DB2 that are asynchronous to the strobe signal.
The control bit passed to the parallel/serial conversion circuit is set to 0. Parallel/serial conversion circuit 13
Then, all the parallel data and control bits latched by the latch circuit 11 are converted into serial data and output to the transmission line. At this time, if the control bit is 0, the data DA1, DA synchronized with the strobe signal
The bit in the packet of the serial data signal corresponding to No. 2 is meaningless dummy data and is removed by a receiving circuit, which will be described later. If the control bit is 1,
All parallel data is meaningful and valid data.

FIG. 2 shows the structure of a packet of serial data signals output from the parallel-to-serial conversion circuit 13 to the transmission line. This packet includes a start bit and control bit for notifying the start of serial data signal transmission, and data DA1 and DA2 that are synchronized with the strobe signal.
and bits corresponding to data DB1 and DB2 asynchronous to the strobe signal. If this packet is sent out by generating a strobe signal, then in Figure 2 (
As shown in b), the control bit is 1, and if done by the strobe watchdog timer, the control bit is 0. Also, the control bit is 0
In this case, the bits corresponding to DA1 and DA2 are dummy.

The receiving section 2 converts the serial data signal output from the transmitting section 3 into a parallel data signal and outputs it. It is composed of a strobe generation circuit 23.

The serial/parallel conversion circuit 21 converts the received serial data signal into a parallel data signal, and passes all data to the latch circuit 22 and control bits to the strobe generation circuit 23.

The data output circuit 22 checks the value of the control bit, and outputs all data when the control bit is 1, and outputs only data asynchronous to the strobe signal when the control bit is 0. As a result, the dummy data generated in the transmitter is removed.

In the strobe generation circuit 23, the serial
The value of the control bit output from the parallel conversion circuit 23 is determined, and when the control bit is 1,
It outputs a strobe signal and does nothing when the control bit is 0.

[0023]

[Effects of the Invention] As detailed above, the parallel
The serial conversion circuit has the following effects.

(1) Since the strobe monitoring timer is provided, the maximum sampling period of data asynchronous to the strobe signal is guaranteed, and data asynchronous to the strobe signal can be reliably transmitted.

(2) Since the latch circuit can immediately latch the parallel data signal when a strobe signal is generated, it is possible to reliably transmit data in synchronization with the strobe signal.

(3) Due to the effects of (1) and (2) above,
Data synchronized with the strobe signal and data asynchronous with the strobe signal can be reliably transmitted using one transmission line.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a parallel-to-serial conversion and transmission circuit of the present invention.

FIG. 2 is a diagram showing the structure of a packet used in the parallel-to-serial conversion transmission circuit shown in FIG. 1, in which (a) shows the packet structure, and (b) and (c) FIG. 3 is a diagram showing sent packets.

FIG. 3 is a diagram showing a parallel-to-serial conversion transmission circuit according to the prior art.

[Explanation of symbols]

1 Transmission section 2 Receiving section 3 Transmission line 11 Latch circuit 12 Strobe monitoring timer 13 Parallel/serial conversion circuit 21 Serial/parallel conversion circuit 22 Data output circuit 23 Strobe generation circuit

Claims (1)

[Claims] 1. A parallel-to-serial conversion transmission circuit that converts parallel data consisting of data synchronized with a strobe signal and data asynchronous to a strobe signal to serial data and transmits the serial data. A strobe monitoring timer that outputs a signal instructing the latch circuit to latch if it does not occur for a predetermined period of time, and a strobe monitoring timer that latches all parallel data and outputs the control bit as 1 when a strobe signal occurs. When a latch instruction is output, there is a latch circuit that latches only data asynchronous to the strobe and outputs the control bit as 0, and converts the control bit output from this latch circuit and the latched parallel data from parallel to serial. A parallel-to-serial converter circuit outputs a serial data signal using a parallel-to-serial converter, a serial-to-parallel converter circuit inputs the serial data signal output from the parallel-to-serial converter and converts it into parallel data, and a It consists of a data output circuit that outputs all parallel data and a strobe signal when the control signal in the parallel data is 1, and outputs only data asynchronous to the strobe signal when the control signal in the parallel data is 0. A parallel/serial conversion transmission circuit featuring the following features.