Chapter 2 Specifications
2 – 9
Specifications of serial communication port are shown in Table 2.8.
Table 2.8 Serial port specifications
Item Specification
Transmission speed 4,800 / 9,600 / 19,200 / 38,400 / 57,600 / 115,200 bps
Interface RS-232C RS-422 RS-485
Maximum cable length 15 m (16.40 yd.) 500 m (546.81 yd.) 500 m (546.81 yd.)
Connection mode
(Maximum connected units)
1 : 1 1 : N (32 units) 1 : N (32 units)
Communication method Half duplex
Synchronization method Start-stop synchronization
Supported function Gateway, General purpose communication, Modbus-RTU master
Transmission method Serial transmission (bit serial transmission)
Transmission code outgoing
sequence
Send out from the lowest bit in character units
Error control Vertical parity check, sum check, overrun check, framing check.
Transmission unit Message unit (variable length)
Maximum message length 1,024 bytes (including control characters)
Caution 1:N communication (RS-485)
It is recommended to add about 5 to 20 ms of waiting time between data receiving from devices and data sending from CPU for
more stable communication.
Caution Serial communication in 115.2kbps
Serial communication in 115.2kbps could be unstable depending on PC. If so, change the baud rate to 57.6kbps or slower.
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