Perle Systems STS, SCS Modbus I/O Access, Modbus TCP Application, Function Codes, PC running a

Modbus I/O Access

Modbus TCP Application

If you have a Modbus RTU or Modbus ASCII program, you can access the I/O by connecting to the

IOLAN over the network.

UID: 15

	Network		perle
PC running a		IOLAN
Modbus RTU
or ASCII
Application

Power

I/O Digital

Output

Modbus I/O Access

The section defines the function codes and registers you will need to access the I/O through Modbus TCP, Modbus serial, or Modbus serial/TruePort.

Function Codes

The following function codes are supported by the IOLAN:

z01 read coils

z03 read multiple holding registers

z04 read input registers

z05 write coil

z06 write single register

z08 diagnostics (echo the request)

z15 force multiple coils

z16 write multiple registers

There are four Modbus data models:

Discrete Input	Not used
Coils	Digital Input (DI), Alarm state for DI, Digital Output (DO). All coils
	are Boolean values and are 1 byte.
Input Registers (IR)	Analog Input (AI), Alarm state for AI. All Input Registers are 2 bytes
	long.
Holding Registers	Status (R), Control value (R/W or W). Holding Registers with _ENG
	registers are 4 bytes long, all other Holding Registers are 2 bytes
	long.

All coil/register values are in decimal.

268 IOLAN SDS/SCS/STS User’s Guide, Version 3.6