IDEC High Performance Series - Manual (Page 640)

Chapter 5
622
External Device Setup Manual
4. Functions
The following section describes the details of the functions.
The communication example listed for each function is only for the 7th and later bytes of the data.
Refer to the description of the basic format and add bytes 0 to 6 in the actual communications.
- FC3 Read multiple registers - Reading of Holding Register (HR) consecutively
- FC16 Write multiple registers - Writing to Holding Register (HR) consecutively
The MICRO/I or Touch supports the following functions.
Function
code Function name Description
3 Read multiple registers Reading of Holding Register (HR) consecutively
16 (10Hex) Write multiple registers Writing to Holding Register (HR) consecutively
1 Read coils Reading of Coil (C) consecutively
2 Read discrete inputs Reading of Input Relay (I) consecutively
4 Read input registers Reading of Input Register (IR) consecutively
5 Write coil Writing to a single Coil (C)
6 Write single register Writing to a single Holding Register (HR)
7 Read exception status Reading of exception status (0 to 7th bit of HR400001)
Request
Byte 7 FC (Function code) = 03
Byte 8-9 Reference No.
Byte 10-11 Number of read words (1 to 125 words)
Normal response
Byte 7 FC (Function code) = 03
Byte 8 Number of bytes of the response (number of read words x 2)
From Byte 9 Read data
Abnormal response
Byte 7 FC (Function code) = 83 (HEX)
Byte 8 Exception code 01 or 02
Example
Reading of HR400001 (1 word). The read value is 1234 (HEX).
03 00 00 00 01 => 03 02 12 34
Request
Byte 7 FC (Function code) = 10 (HEX)
Byte 8-9 Reference No.
Byte 10-11 Number of write words (1 to 100 words)
Byte 12 Number of write bytes (2 x number of write words)
From Byte 13 Write data