Perle Systems IOLAN SCS - Manual (Page 276)

Accessing I/O Data Via TruePort
276 IOLAN SDS/SCS/STS User’s Guide, Version 3.6
Format of API Commands
There are two groups of commands:
z Get Commands—Retrieve values of the I/O channel registers
z Set Commands—Set values on the I/O channel registers.
I/O Channel registers are all assigned unique addresses, which need to be referenced in all of the
commands. Please refer to the documentation specific you the applicable mode, for the list and
addresses of all the registers.
Get Commands
The following tables show the general structure to be used for Get commands.
Command Format
Response Format
Note: All commands need to be written to the COM port as a single write.
Model Go to...
A4 A4/T4 Registers on page 270
T4 A4/T4 Registers on page 270
A4D2 A4D2/A4R2 Registers on page 271
A4R2 A4D2/A4R2 Registers on page 271
D4 D4/D2R2 Registers on page 272
D2/R2 D4/D2R2 Registers on page 272
Note: Numeric values provided in the API documentation are in Hexadecimal (Hex) format.
Byte(s) # of Bytes Value
1 1 Command Code:
z 0x01 – Get “coils” (Boolean register)
z 0x03 – Get “holding registers” (R/W registers)
z 0x04 – Get “input registers” (R only register)
2-3 2 Starting register number (see A4/T4 Registers on page 270 ,
A4D2/A4R2 Registers on page 271 , or D4/D2R2 Registers on page 272
for this value).
4-5 2 Number of registers to read. If this value is greater than 1, the response
will contain the values of multiple consecutive registers.
Byte(s) # of Bytes Value
1 1 Command that this is a response to. If an error has been detected, the
command value will have the high bit set (OR with 0x80). For
example: The command is 0x04, so the command field in the response
would be 0x84.
2 1 Length of data (in bytes) starting in next byte.
3-n n Requested register values.