JPH0214824B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of the Invention The present invention relates to a data transmission device in which a slave station transmits data in response to a polling signal from a master station.

(2) Prior Art As a slave station, there is a calculation device such as a digital controller that collects process variables such as temperature, performs predetermined calculations, and generates control signals and the like. Then, suppose that the slave station has to transmit predetermined data in response to an interrupt signal from the master station.
The slave station had to perform two functions at the same time: data collection and calculation and communication with the master station, which increased the burden on the slave station and made it difficult to quickly transmit and process data. .

(3) Purpose of the Invention In view of the above points, the purpose of the present invention is to provide a data transmission device that enables rapid and reliable data transmission.

(4) Embodiment of the Invention FIG. 1 is a configuration diagram showing an embodiment of the invention.

1 is the main station, and 21, 22, and 23 are slave stations consisting of arithmetic devices such as digital controllers that take process variables such as temperature as input, compare them with set values, and generate predetermined control outputs. Slave station 21, 22, 2
3 through a transmission line l.

Here, the data collected by master station 1 is
1, 22, 23, input values, setting values, etc., which can be arbitrarily determined in advance, and the data can be sent in sequence in response to polling from the main station 1. Necessary data can be collected quickly. Note that the data to be transmitted during polling can be arbitrarily selected, stored in memory, or set using a setting switch.

In other words, as shown in Fig. 2, in response to polling signals P ₁ , P ₂ , P ₃ , P ₁ , ... from the master station, the slave stations 21, 22, 23 respond to predetermined measurement values and settings. Data content that changes such as value TEXT
are sequentially transmitted to the main station 1 one by one for each polling. The master station 1 is connected to the slave stations 21 and 2.
When data 2 and 23 are received, an acknowledgment signal is sent.
Generates an ACK.

Next, the master station 1, for example, tells a specific slave station 21,
When you want to read or write special data, do the following. As shown in Figure 3, instead of a normal polling signal, a transfer request signal or a write request signal P ₁ TEXT READ (WRITE) is sent to the slave station 2.
1 and interrupt, and the slave station 21 generates an acknowledge signal (ACK). Then, in response to the next polling signal _P1 , the slave station 21 transmits the request data TEXT or the written data.
Answer backup TEXT. When the interrupt ends, normal operation resumes.

Note that when write requests are received continuously from the master station 1, the slave station 21 writes the contents one after another, and with the last polling signal,
Unbacks only the last written data.

FIG. 4 shows an overview of the arithmetic unit 21. The first microcomputer 221 receives process variables such as temperature as input, performs comparison calculations with set values, generates control outputs, and outputs various set values and the latest information. It is operative to store the input value in the first memory _M1 . The second microcomputer 222 receives the polling signal _P1 etc. from the main station 1, and also receives the first memory _M1 of the first microcomputer 221.
From there, only data arbitrarily determined in advance is stored in its own second memory _M2 and transmitted.

For example, when a transfer request is received from the main station 1, the second microcomputer 222 sends an acknowledgment signal.
Sends the ACK to the outside, and stores the required data from the first memory _M1 of the first microcomputer 221 in its own second memory _M2 ,
The next polling signal sends this data to the main station 1.
I am trying to transfer it to.

In other words, by doing this, the burden on the slave station becomes much lighter, and the master station can collect the latest data at high speed.

(5) Summary of the Invention In this invention, in normal times, a slave station transmits data predetermined to be transmitted in response to a polling signal from a master station, and receives data that is specifically required from the master station. When a transfer request or write request is received, the data transmission device transmits or answers the requested data at the next polling.

(6) Effects of the invention Since the upper main station collects only predetermined data, it is possible to collect data quickly.

When a data transfer request is made, the data is not transferred immediately, but is transferred with the next polling signal, allowing time leeway, which reduces the burden on lower-level slave stations and provides the latest data can be collected.

Data writing is confirmed by the answer check, so it is accurate.

[Brief explanation of drawings]

1 and 4 are configuration explanatory diagrams showing one embodiment of the present invention, and FIGS. 2 and 3 are signal diagrams for explaining the operation. 1...Main station, 21, 22, 23...Slave station, l...
...transmission line.

Claims (1)

[Claims] 1. In a data transmission device in which a plurality of slave stations transmit data in response to a polling signal from a master station, the slave stations normally transmit data in advance in response to a polling signal from the master station. When the master station sends arbitrarily specified data and requests to transfer or write particularly required data, the requested data is sent or the written data is answered during the subsequent polling of the slave station. This data transmission device is characterized in that it is configured to perform back-up. 2. The data transmission device according to claim 1, wherein the slave station continuously writes data when write requests are continuously received from the master station.