JPH0252466B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a polling method. This invention relates to an improvement in a data transfer method that transfers data using a selecting method.

Figures 2a and 2b show examples of line configuration diagrams.

In FIG. 2a, a plurality of slave stations 1...n are connected in tandem with a master station, for example, at both ends, whereas in FIG. 2b, the master station is connected only at one end, forming a loop.

However, in either case, data is sent and received by polling. This is done by the selection method, so
Only slave stations called by the master station send data to the master station.

For this reason, the receiver of each slave station is connected to the line so that it can receive calls from the master station at any time, but normally the contacts of switch 1-1... are turned to the loop side as shown in the figure. Only when a call is received, it switches to the talk side and sends data to the master station.

Note that solid line arrows and dotted line arrows in FIGS. 2a and 2b indicate the flow of a call signal and the corresponding data, respectively.

The data transmission method between each station is, for example, a start-stop synchronization method in which the interface is simple and the phase relationship of the clocks can be ignored.

FIG. 3 shows the format of the start-stop synchronization method.

In the figure, when there is no data, it is at H level, but when it changes to L level, a start bit STR indicating a start is sent.

After that, data _D0 to D6 that change between H and L level depending on the contents follow, and the parity bit P
After inserting the bit, set 1 to 2 bits to H level and send out the stop bit STP indicating completion.
The character is completed. This process is repeated to send one character at a time to, for example, the master station.

On the other hand, on the receiving side, the read clock is raised at the fall of the start bit STR, and the start bit is
First, read the level at point a of the STR half cycle. After that, the level of the specified number of bits (for example, 11 bits) is read one cycle at a time.

At this time, the start bit STR goes to H level,
It is confirmed that the parity bit P is correct, and it is determined that this character has been received normally.

Here, poll as described above. Since data is sent and received using the selecting method, if a slave station that is not called by the master station urgently desires to send data, there are the following methods.

Wait for yourself to be called.

After transmitting a code indicating an emergency to other slave stations and establishing a transmission path with the master station, data is transmitted.

One of these methods must be selected, but as shown below, it takes time to send data, and it is difficult to send data urgently.

Therefore, there is a need for a data transfer method that can send data in a shorter time.

[Conventional technology]

FIG. 4 shows a block diagram of a conventional example.

In the transmitting section shown in the figure, a computer (hereinafter abbreviated as CPU) 13 reads data from each terminal 10 connected to an input/output port 11 and writes it into a memory 12.

Next, the data read from the memory 12 is converted into, for example, JIS 7 code using a program.
After being converted to JIS 7 code by CPU13,
The parallel/serial conversion circuit 14 converts it into a serial code.

If there is a call from the slave station, the switch control circuit 15 switches the switch 1 to the talk side.
-1 to the master station.

In the receiving section, the received serial code is converted into a parallel code by the serial/parallel conversion circuit 16, and then returned to the original data by the CPU 13 using a JIS 7 code decoding program, and once written into the memory 12. , drives the terminal 10 via the input/output port 11.

Note that the parallel/serial conversion circuit 14 and the serial/parallel conversion circuit 16 are implemented as an LSI, and the start bit STR, parity bit P, and stop bit STP in the format shown in FIG. Processes D ₀ to D6 are performed.

[Problem that the invention seeks to solve]

As explained above, polling from the master station. There is no problem when transmitting data in a dependent manner using the selecting method, but if you wish to send emergency data from a slave station, you must set all the switches of the slave stations that are on the talk side to the loop side. Data cannot be sent because the line is not established.

Therefore, in order to establish a line, a specific pattern is sent to the slave station on the talk side. For example, in the #1 slave station, after performing serial/parallel conversion as described above, the CPU 13 recognizes this specific pattern. Since you will be moving the switch to the loop side,
Due to the long processing time, the above-mentioned specific pattern disappears at the #1 slave station and is not sent to the next #2 slave station.

Therefore, it is necessary to further transmit the same specific pattern for the #2 slave station to cause the switch to change over.

That is, the data must be sent after sequentially sending out a plurality of specific patterns in consideration of conversion and CPU processing time in each slave station.

Of course, even with the method of waiting for a call, it takes time to send the data.

No matter which method is used, there is a problem in that it takes time to send the data.

[Means for solving problems]

The above problem is that each slave station has a means for sending a specific pattern onto the transmission path, a means for detecting the specific pattern from the received signal, and a connection path for sending the signal from the own station onto the transmission path. At the same time, a switch is installed to disconnect the transmission line from the downstream station to the previous station, and by detecting a specific pattern from other slave stations, if the switch in the own station is operating, it can be restored and then restored. This problem is solved by the data transfer method of the present invention, which preferentially establishes a transmission path between a local station and a previous station.

[Effect]

The present invention speeds up the control of the switch circuit by using a specific pattern detection circuit to detect a specific pattern from a slave station, which was previously done using software in the CPU.

That is, when a received serial code of, for example, 7 bits all 0 is detected by a specific pattern detection circuit,
The detection output from this circuit prohibits the CPU from controlling the switch and forcibly switches the switch to the transmission line side.

This speeds up the switching of the switch, so emergency data can be sent out quickly.

〔Example〕

FIG. 1 shows a block diagram of one embodiment of the invention. Note that the same reference numerals indicate the same objects throughout the figures.

In the figure, a specific pattern detection circuit 1 in the receiving section of a slave station in which a specific code added to the receiving section, for example, a code of 7 bits all 0, has fallen to the talk side.
Added to 7.

This circuit 17 compares it with a specific pattern that it owns, for example, and if it matches, outputs a specific pattern detection signal to an AND circuit 18.

On the other hand, even if the output of the switch control circuit 15 controlled by the CPU 13 is applied to the AND circuit 18, the output of the specific pattern detection circuit 17 is given priority, so the output of the switch control circuit 15 is blocked. , the switch circuit 1-1 is pushed to the transmission path side by the output of the specific pattern detection circuit.

However, the state of switch 1-1 at that time is CPU
can be read into.

For example, if data code-converted by the CPU is being sent to the master station via switch 1-1 and the switch is forcibly switched, the transmission from the CPU will be temporarily stopped and the emergency data will be sent to the master station. This is to send the remaining data after passing through the data first.

In addition, the specific pattern must be selected so that it does not match words in other telegrams.

〔Effect of the invention〕

As explained above, the present invention reduces the time required to change the switch by detecting a specific pattern using hardware, so that emergency data can be sent in a shorter time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
Figures a and b are line configuration diagrams, Figure 3 is a format diagram of an asynchronous system, and Figure 4 is a block diagram of a conventional embodiment. In the figure, 13 is a CPU, 14 is a parallel/serial conversion circuit, 15 is a switch control circuit, 16 is a serial/parallel conversion circuit, 17 is a specific pattern detection circuit, and 18 is an AND circuit.

Claims (1)

[Claims] 1 Polling. In a transmission system that transfers data from a slave station to a master station using a selecting method, each slave station has a means for sending a specific pattern onto a transmission path, a means for detecting the specific pattern from a received signal, and a means for transmitting a specific pattern from the own station. A connection path is formed to send signals to the transmission path, and a switch is provided to disconnect the transmission path from the downstream station to the preceding station. A data transfer method that is characterized in that when the station is in operation, it is restored and a transmission path between the downstream station and the preceding station is established preferentially.