User`s guide

Copyright © 2004 EIM COMPANY, INC. • 13840 PIKE ROAD • MISSOURI CITY, TX. 77489
Page 119
Controlinc 1746-C (Version 5.21) Network Master Users Guide (2004-11-18)
Example (in byte order) of a request to read
registers 40108 – 40110 (internal holding
registers 107 – 109) from slave device 17:
1. Slave Address 11
2. Function 03
3. Starting Address Hi byte 00
4. Starting Address Lo byte 6B
5. No. of Registers Hi byte 00
6. No. of Registers Lo byte 03
7. CRC Hi byte ––
8. CRC Lo byte ––
NOTE: 107 decimal is 0x6B
6.5.2.2. Modbus Function Code 03 … Read Holding Register
Using function code 03, the Modbus master (host) may directly address and read any memory register in
the actuator. This includes all registers containing discrete values (inputs & coils).
Refer to the previous section that describes the “
Addressable Holding Registers”.
Response example (in byte order):
1. Slave Address 11
2. Function 03
3. Byte Count 06
4. Data Hi (Register 40108) 02
5. Data Lo (Register 40108) 2B
6. Data Hi (Register 40109) 00
7. Data Lo (Register 40109) 00
8. Data Hi (Register 40110) 00
9. Data Lo (Register 40110) 64
10. CRC Hi byte ––
11. CRC Lo byte ––
The contents of register 40108 are shown as the two
byte values of 02 2B hex (or 555 decimal).
The contents of registers 40109–40110 are 00 00 and
00 64 hex, or 0 and 100 decimal.