Perle Systems 5500161-40 manual Modbus I/O Access, Modbus TCP Application, Function Codes

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.

Network

PC running a Modbus RTU or ASCII Application

UID: 15

perle

IOLAN

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.

278 IOLAN SDS/SCS/STS/MDC User’s Guide, Version 4.0