JP2623816B2 - Signal transmission method - Google Patents

Description

The present invention relates to a signal transmission between a communication microcomputer for controlling signal transmission between a plurality of remote controllers such as a hot water supply system and a control microcomputer for controlling terminals such as remote controllers. It is about the method.

(Prior Art) In a conventional signal transmission system, for example, a main microcomputer 2 for controlling signal transmission in a circuit as shown in FIG. Seventh sub-microcomputer 1 controlling the terminal
Using the serial transmission circuit built into the microcomputer shown in the figure,
The data transmitted from the sub-microcomputer 1 is transmitted according to the procedure shown in FIG.
Was sent to.

The transmission procedure is as follows. In the case of transmission from the main microcomputer 2 to the sub-microcomputer 1, as shown in FIG. Sub-microcomputer 1 detects FL at START and detects FLG at 19
Lo. When the main microcomputer 2 detects Lo of FLG, it sets 1 byte of data in the serial buffer and sets CLK at 20.
And to the main data line DM. When the 1-byte serial transmission ends, the sub-microcomputer 1 takes out the transmitted data from the serial buffer and sets the FLG to Hi at 21.
Check START. If START is Lo, FLG is set to Lo as shown at 22 to receive the next byte. twenty three
If START is set to Hi as shown in FIG.

The transmission procedure is substantially the same as that of FIG. 5 when the transmission from the sub-microcomputer 1 to the main microcomputer 2 is performed, as shown in FIG. The only difference from FIG. 5 is that the data transmission at 20 is performed on the sub data line DS.

The serial transmission circuit built in the microcomputer has a serial buffer 24 composed of an 8-bit shift register as shown in FIG. 7, and the data in the serial buffer is transmitted from a serial output terminal 26 by a clock from an oscillation circuit 25. The data is output and the input data is taken into the serial buffer from the serial input terminal 27. The clock pulse is counted by a 3-bit counter 28, and an interrupt signal is issued when one byte of serial transmission is completed.

The main microcomputer 2 which performs communication control by this method can communicate variable-length data in units of 8 bits in two directions. Also, the data transmission request is generated asynchronously.
However, even if START is set to Lo, if the FLG Lo is not detected within a certain period of time, START is set to Hi. At this time, if the main microcomputer 2 sets START to Lo, the sub-microcomputer 1 detects START Lo and performs reception.

(Problems to be Solved by the Invention) However, in the above configuration, when a signal transmission request occurs simultaneously in both the main microcomputer 2 and the sub-microcomputer 1, the handshake at the start of communication ends without waiting for a timeout of the sub-microcomputer 1. Did not. Originally, the main microcomputer 2 is a communication-dedicated microcomputer that mainly performs communication control, and the sub-microcomputer 1 is mainly used for processing other than communication, and it is often necessary to reduce processing related to communication. However, since handshaking may take a long time in normal communication, there is a problem in that the amount of main processing is limited accordingly.

Further, the main microcomputer 2 is often realized by a relatively small microcomputer (ROM size of about 1 Kbyte) as a communication interface. However, although a small microcomputer has a built-in serial transmission circuit, the frequency of the serial transmission clock is inevitably increased to several hundred KHz due to the small frequency division of the serial transmission clock, which imposes mounting restrictions such as shortening the signal transmission path as much as possible. However, the signal transmission reliability was disadvantageous.

An object of the present invention is to solve such a conventional problem, to shorten the time required for handshaking, to reduce the communication processing load on the sub-microcomputer 1 as much as possible, and to realize highly reliable signal transmission at lower cost. I do.

(Means for Solving the Problems) In order to solve the above problems, a signal transmission system according to the present invention comprises:
An 8-bit variable-length bidirectional serial signal transmission between a main microcomputer with a built-in serial transmission circuit and a sub-microcomputer with a built-in serial transmission circuit that generates a signal transmission request asynchronously, using two dedicated handshake lines and a clock Using five lines, a main data line that transmits data from the main microcomputer to the sub microcomputer, and a sub data line that transmits data from the sub microcomputer to the main microcomputer. A transmission start handshake is performed using one of the lines, the main data line and the sub data line to determine a transmission terminal and a reception terminal, and then a byte is determined using two dedicated handshake lines and a data line on the reception side. The transmission handshake is performed for each byte.

The transmission start handshake outputs a request signal to the main data line when a signal transmission request is issued to the main microcomputer, and outputs a request signal to the sub data line while detecting the main data line when a signal transmission request is issued to the sub microcomputer. When the sub microcomputer detects the request signal on the main data line, it stops the request signal sent to the sub data line, and the main microcomputer detects the sub data line only when it does not output the request signal. The reception signal is output to a predetermined handshake dedicated line, the sub-microcomputer always detects the main data line, and outputs the reception signal to the predetermined handshake dedicated line when detecting the request signal.

Still further, the byte transmission handshake outputs a signal from the start of transmission to the first handshake dedicated line until transmission of all transmission data is completed, and the transmission side outputs a signal to the second handshake dedicated line from the start of one byte transmission to the end of one byte transmission. The receiving side outputs a byte transmission permission signal to the data line while the signal is being output to the first dedicated handshake line.

(Operation) According to the present invention, even if a signal transmission request is generated at the same time, the signal can be immediately detected by detecting the request signal.
Handshake always ends in a short time.

Further, by using the data line on the receiving side for the byte transmission handshake, the clock can be output from only one of the terminals.
Even if an inexpensive one of about 1 Kbyte is used and the frequency division of the clock is not sufficient, highly reliable signal transmission can be performed using only the clock of the sub-microcomputer 1 which can sufficiently divide the clock.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram of a communication circuit according to the present invention. In FIG. 4, the clock is bidirectional, whereas in FIG. 1, the clock is output only from the sub-microcomputer 1. The main data line DM is connected to an external interrupt terminal of the sub microcomputer 1.

FIG. 2 is a diagram showing a transmission procedure when a signal is transmitted from the main microcomputer 2 to the sub-microcomputer 1. First, the main microcomputer 2 sets the main data line DM to Lo at 3. When the sub-microcomputer 1 detects DM Lo at the external interrupt terminal,
To Lo. When the main microcomputer 2 detects Lo of FLG, it sets DM to Hi at 5. When the sub-microcomputer 1 detects Hi of DM, it sets FLG to Hi at 6 and ends the signal transmission start handshake. Next, the main microcomputer 2 sets START to Lo at 7. When the sub-microcomputer 1 detects Hi of FLG and Lo of START, it sets the sub-data line DS to Lo at 8. Main microcomputer 2
When the DS Lo is detected, the transmission data is set in the serial buffer, the FLG is set to Lo at 9 and the byte transmission handshake is completed. When the sub-microcomputer 1 detects Lo of FLG, it sets FFh in the serial buffer to permit serial interrupt, activates the serial transmission circuit, and performs main processing. The subsequent byte transmission handshake is performed in the serial interrupt. Therefore, signal transmission can be performed in parallel with little effect on the main processing. When the transmission of one byte is completed, the main microcomputer 2 sets only the FLG to Hi as indicated by 10 when there is still transmission data. If all transmission data has been sent, ST as shown in 11
After setting ART to Hi, set FLG to Hi. The sub-microcomputer 1 takes out the transmission data of the serial buffer, detects Hi of FLG and detects Lo of START, and performs the byte transmission handshake again as in the case of the first byte. If Hi of FLG is detected and Hi of START is also detected, signal transmission is terminated there.

Next, a transmission procedure from the sub microcomputer 1 to the main microcomputer 2 will be described with reference to FIG. Both the signal transmission start handshake and the byte transmission handshake are performed in exactly the same manner except that the transmitting side and the receiving side are switched. In the byte transmission handshake, the sub-microcomputer 1 detects that the main microcomputer 2 has changed DM to Lo in 12 and sets transmission data in the serial buffer and 13 sets FLG to Lo in 13. When the sub-microcomputer 1 detects that the DM of the main microcomputer 2 has been set to Hi at 14, the sub-microcomputer 1 activates the serial transmission circuit to transmit 1-byte data.

As described above, DM is provided for the signal transmission request of the main microcomputer 2 and DS is provided for the signal transmission request of the sub-microcomputer 1 in the signal transmission start handshake, so that it is possible to instantaneously detect whether or not a transmission request is occurring at the same time. Therefore, no time loss occurs in handshaking. In addition, since both DM and DS are used, there is no need to add a handshake line.

In the byte transmission handshake, the data line on the receiving side, which was not used in the conventional example, is also used as the handshake line, so that the clock can always be sent from either side. The best one can be selected from the frequencies.

(Effects of the Invention) As described above, according to the signal transmission method of the present invention, the following effects can be obtained.

(1) Even if requests are generated at the same time in the signal transmission start handshake, instantaneous detection is possible, so that the time required for the handshake is always short, so that more time can be allocated to the main processing.

(2) Since a configuration in which the signal transmission clock is output from either one can be adopted, the range of selection of the clock frequency is widened, and the reliability of signal transmission can be improved by using a clock having a more optimal frequency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit block diagram for explaining a signal transmission system according to an embodiment of the present invention, and FIGS. 2 and 3 are diagrams for explaining a signal transmission procedure of the embodiment. FIG. 4 is a circuit block diagram for explaining a conventional signal transmission system, FIGS. 5 and 6 are time charts for explaining a signal transmission procedure of the conventional example, and FIG. 7 is the present invention. FIG. 9 is a configuration diagram of a serial transmission circuit built in a microcomputer commonly used in the embodiment of the present invention and the conventional example. 1 ... Sub microcomputer, 2 ... Main microcomputer.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Genmichi Kato 1006 Kadoma, Kazuma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Koichi Ueki 1006 Kadoma, Kazuma, Kadoma, Osaka Matsushita Electric Industrial Co., Ltd. Inside

Claims (3)

(57) [Claims] 1. A main microcomputer having a serial transmission circuit which generates a signal transmission request asynchronously (hereinafter referred to as a main microcomputer) and a sub-microcomputer having a serial transmission circuit built therein (hereinafter referred to as a sub-microcomputer).
A variable-length bidirectional serial signal transmission system in units of 8 bits, comprising two dedicated lines for handshaking, a clock line, a main data line for transmitting data of the main microcomputer to a sub-microcomputer, Is transmitted using one of the two dedicated handshake lines, the main data line and the sub data line at the start of signal transmission, using five sub data lines for transmitting the data to the main microcomputer. After the start handshake is performed and the transmission terminal and the reception terminal are determined, the byte transmission handshake is performed using the two dedicated handshake lines and the data line on the reception side.
Signal transmission method for each byte. 2. A transmission start handshake outputs a request signal to a main data line when a signal transmission request is issued to a main microcomputer, and requests a sub data line while detecting the main data line when a signal transmission request is issued to a sub microcomputer. The sub-microcomputer detects the request signal on the main data line, stops the request signal being output on the sub-data line, and outputs the sub-data line only when the main microcomputer is not outputting the request signal. , And when a request signal is detected, a reception signal is output to the predetermined line dedicated to handshaking. The sub-microcomputer always detects the main data line. The signal transmission method according to claim 1, wherein the signal transmission method outputs a signal. 3. The transmitting side of the byte transmission handshake is first.
From the start of transmission to the end of transmission of all transmission data to the dedicated handshake line, and outputs a signal from the start of one byte transmission to the end of one byte transmission to the second dedicated handshake line. 2. The signal transmission system according to claim 1, wherein a byte transmission permission signal is output to the data line while the signal is being output to the dedicated handshake line.