Modbus Function Codes - YASKAWA IM 053MT Manual

VIPA System SLIO
4.10

Modbus function codes

Naming convention
Range definitions
Overview
Code Command
01h Read n Bits
02h Read n Bits
03h Read n Words
HB300 | IM | 053-1MT01 | en | 19-40
Modbus has some naming conventions:
n Modbus differentiates between bit and word access; Bits = "Coils" and Words = "Reg-
ister".
n Bit inputs are referred to as "Input-Status" and bit outputs as "Coil-Status".
Word inputs are referred to as "Input-Register" and word outputs as "Holding-Reg-
n
ister".
Normally the access with Modbus happens by means of the ranges 0x, 1x, 3x and 4x.
0x and 1x gives you access to digital bit areas and 3x and 4x to analog word areas.
For the VIPA modules is not differentiating digital and analog data, the following assign-
ment is valid:
0x - Bit area for master output
Access via function code 01h, 05h, 0Fh
1x - Bit area for master input
Access via function code 02h
3x - Word area for master input
Access via function code 04h, 17h
4x - Word area for master output
Access via function code 03h, 06h, 10h, 16h, 17h
With the following Modbus function codes a Modbus master can access a Modbus slave.
The description always takes place from the point of view of the master:
Description
Read n bits of master output area 0x
Read n bits of master input area 1x
Read n words of master output area 4x
Deployment
Modbus function codes
69