JPS6365731A - Polling system - Google Patents

Abstract

PURPOSE:To reduce a data collection time by applying weighting by a slave station to a request signal sent from each slave station in a polling system of a system using a serial bus so as to allow a master station to discriminate a request sender quickly. CONSTITUTION:A slave station (i) (i=1-n) is provided with a serial/parallel I/O port 15 processing a data in series with a current INF 10 and in parallel with a CPU 12 in addition to the current INF 10 and the CPU 12. Moreover, a weighting resistor Ri causing a current I=V/Ri to flow in turning on a transistor TRi is connected to a request bus REQ-BUS. The CPU 12 of a master station O fetches a digital value from a converter 13 through a parallel I/O port 14 to apply polling processing to it. After discriminating a save station supplying a request signal, the master station applies polling to the slave station through a TX-BUS to receive the data from the slave station through an RX- BUS.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a polling method for a system using a serial bus, and in particular, the present invention weights a request signal sent from a slave station to a master station to It facilitates identification.

[Conventional technology]

In the system polling method using a serial bus,
A slave station that has data to send may send a request signal to the master station to request data collection. However, since the request signal has two values of H (high) and L (low), it is impossible to determine which slave station it is from. For this reason, the master station must collect data by polling each slave station in turn, which has the disadvantage that it takes time to collect data from slave stations with lower priority.

[Problem that the invention seeks to solve]

The present invention makes it possible to easily identify the slave station that has issued the request signal by weighting the request signal sent from the slave station to the master station differently for each slave station.

[Means for solving problems]

The present invention provides a polling method for a system in which a master station and a plurality of slave stations are connected via a serial bus, and the slave stations transmit request signals to the master station through the request bus. This is characterized in that a weighted current is applied to each slave station to generate the request signal.

[Effect]

If the request signal sent by each slave station is weighted uniquely to the slave station, the master station receiving the request signal can quickly and easily recognize which slave station has requested polling. Therefore, data collection time is significantly shortened compared to the conventional method in which slave stations that do not issue request signals are also polled.

〔Example〕

FIG. 1 is a system configuration diagram showing an embodiment of the present invention.
is the master station, 1 to n are slave stations, and RX-BUS.

TX-BUS and REQ-Bus are serial buses.

RX-BUS is used when receiving data at master station 0, and T
X-BUS is used when transmitting data from master station 0.

Since these buses are of the current loop type, the transmitting and receiving ends are configured with a current interface (INF) 10. The master station 0 connects this current INFIO, a serial I10 (input/output) port 11 that sends and receives serial bus data, a CPU (1-chip microcomputer) 12 that controls communication, and a request signal (current It consists of a converter 113 that converts a value (value, input, etc.) into a digital value, and a parallel 110 port 14 for input. Slave station 1 (i=1~n
) is equipped with a series/parallel I10 port 15 that processes data in series with the current rNF10 and in parallel with the CPU 12, in addition to the similar current INFIO and CPU12, and also has a transistor Tri for the request bus REQ-BUS. Weighting that causes a current 1=V/Ri to flow when turned on is done by connecting a resistor Ri. Resistance R1, R2゜ of each slave station
...Rn is set as follows, for example.

R+=R/n R2=R/(n-1) RntaR Therefore, if transistor Tr+ is turned on, I=nV/
R, and if transistor Tr2 is turned on, 1=
(n-1)V/R. Similarly, if the transistor Trn is turned on, I=V/R. (2) is the voltage of the power supply at the master station 00 pJ, and a current I flows from the power supply to the ground through the resistor Ri and the transistor Tri.

The CPU 12 of the master station O takes in the digital value from the converter 13 through the parallel I10 port 14 and performs polling processing as shown in FIG. When the slave station that issued the request signal is determined, the slave station is polled through the TX-BUS, and data from the core slave station is received through the RX-BUS.

It is conceivable that two or more slave stations may issue request signals at the same time, but in that case, the program is designed so that the slave station with the smaller resistance value has priority. For example, if the transistors T r + r T r 2 are turned on at the same time, the current I becomes larger than nV/R, so polling is applied to the slave station l side having a smaller resistance value. Therefore, slave station 2 only has to keep transistor Tr2 on until it is polled, and even if transistors Tr3 and below turn on during this time, if transistor Tr+ turns off, 1=(
n-1) Since it becomes more than V/R, the slave station 2 is polled next.

〔Effect of the invention〕

As described above, according to the present invention, in the polling method of a system using a serial bus, the request signal issued by each slave station is weighted on the slave station side, so that the master station can quickly determine the request source. This has the advantage of shortening data collection time.

[Brief explanation of drawings]

Fig. 1 is a system configuration diagram showing one embodiment of the present invention;
The figure is a flowchart showing the polling process of the master station. In the figure, O is a master station, 1 to n are slave stations, and RX-BUS. TX-BUS is a serial bus for transmitting and receiving data, REQ
-BUS is a request bus, R+-Rn is a weighted resistance, and Tr+"Trn is a request transistor.

Claims (1)

[Claims] In the polling method of a system in which a master station and multiple slave stations are connected via a serial bus, and the slave stations transmit request signals to the master station through the request bus, each slave station weights the request bus for each slave station. A polling method is characterized in that a current is passed through and used as the request signal.