Nor-Cal SDC15 Controller - Manual (Page 180)

• 1-frame end judgment
A message end (1-frame end) is determined when a time period specified for
each transmission speed has passed during which no character is received. It is
considered that 1 frame has ended when the next character is not received before
the time-out time shown below passes.
However, the time-out time has a fluctuation of ±1 ms from the values in the
table below.
■ Command type
There are two command (send message) types as shown below:
■ Other specifications
• Supporting the MODBUS Class 0
• Abnormal termination codes
• Maximum number of communications data words
• Other
For the details of MODBUS specifications,
refer to OPEN MODBUS/TCP SPECIFICATION (Release 1.0) by
Modicon Inc.
8-6
Chapter 8. MODBUS COMMUNICATIONS FUNCTIONS
Set transmission speed Time-out time
(bps)
4800 16ms or more
9600 8ms or more
19200 4ms or more
38400 2ms or more
Command Description
ASCII RTU (binary)
Read command "03" (sample) 03H (sample)
Write command "10" (sample) 10H (sample)
Code Description
01 Command error
02 Address error
03 Data error
Data count ASCII RTU
03 (READ) 16 16
16 (WRITE) 16 16