FC6A S
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ANUAL
FC9Y-B1730 7-1
7: DATA LINK COMMUNICATION
Introduction
This chapter describes the data link communication function used to set up a distributed control system.
Data link communication can be used by setting port 1 of the FC6A Series MicroSmart to RS485 or by using an RS485
communication cartridge in port 2 or port 3.
In data link communication, data can be exchanged between a master station and slave stations by connecting a maximum of 31
slave station FC6A Series MicroSmarts to a master station FC6A Series MicroSmart. The master station has a total of 13 words
worth of data registers for each slave station: 6 words for sending data to the slave station, 6 words for receiving data from the
slave station, and 1 word for the communication status/error. Each slave station has a total of 13 words worth of data registers: 6
words for sending data to the master station, 6 words for receiving data from the master station, and 1 word for the
communication status/error.
Data link communication proceeds independently of the user program execution, and the data registers for the data link
communication are updated at the END processing.
The FC6A Series MicroSmart data link function is compatible with the data link functions of the MicroSmart FC5A Series and FC4A
Series.
One CPU module can be either a master station or a slave station. Data link master and slave cannot be used at the same time.
Data Link Specifications
Data Updating
The master station sends the appropriate amount of data (in units of words) to the slave stations. The slave stations that received
this transmission send an amount of data matching the number of words received to the master station. In this way data is
exchanged. The data refresh is performed on the master and slave stations during the END processing. The master station can
only exchange data with one slave station during one communication cycle.
If 31 slave stations are connected, the master station requires 31 communication cycles to exchange data with all slave stations.
The master station turns on the communication complete relay for only one scan after the completion of the communication cycle
with a slave station.
Mode Details
Electric Specifications Compliance with EIA RS485
Baud Rate 19,200, 38,400, 57,600 bps
Synchronization
Start-stop synchronization
Start bit: 1
Data bits: 7
Parity: Even
Stop bit: 1
Communication Cable Shielded twisted pair cable
Maximum Cable Length 200 m (656 feet)
Maximum Slave Stations 31 slave stations
Transmit/Receive Data
Transmit data: 186 words maximum, Receive data: 186 words maximum
0 through 6 words each for transmission and receiving per slave station
Mode Details
Effect on Scan Time
Communication processing between masters and slaves is not synchronized with the user program, and
there is no effect on the scan time.
Data Update Timing
Data updating for both masters and slaves is performed in END processing. The update timing can be
checked with the communication completed flag.
Master-compatible Models FC6A Series MicroSmart (FC4A Series MicroSmart/FC5A Series MicroSmart)
Slave-compatible Models FC6A Series MicroSmart (FC4A Series MicroSmart/FC5A Series MicroSmart)
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