Appendix C: Modbus Data Features - Honeywell S7800A Installation Manual

APPENDIX C: MODBUS DATA FEATURES

See Appendix A page 25 for Setup.
OPERATION
TM
The S7800 ModBus Data Feature enables terminal 1, 2 to
Data and Data -. Table 9 provides register mapping. It
identifies the mapping of the 7800 SERIES parameters to
TM
ModBus registers.
Function
Slave Address Code
01 03
Slave Address Function Code
01 03
Table 11. Query Message Format for Function Code 6 (Broadcast is supported by using a slave address of 00).
Slave Function
Address Code
01 06
Table 12. Response Message Format for Function Code 6 (There is no response if the query was broadcast.)
Slave Function
Address Code
01 06
Table 13. Query Message Format for Function Code 17.
Slave Function
Address Code
03 11
NOTE: See Table 18 for function code 17 response format.
Table 14. Exception Response Message Format.
Slave Function Exception
Address Code Code
80h
Table 9. Query Message Format for Function Codes 3 and 4.
Starting Starting
Address High Address Low
00 0A
Table 10. Response Message Format for Function Codes 3 and 4.
Byte Count
02 00
Starting Starting
Address High Address Low
00 7F
Starting Starting
Address High Address Low
00 7F
CRC CRC
C1 4C
CRC CRC
7800 SERIES S7800A KEYBOARD DISPLAY MODULE
Function Codes
Supported function codes of Modbus Protocol Reference
Guide (PI-MBUS-300 Rev. J) are 3, 4, 6, and 17. Function
codes 3 and 4 are treated the same by the S7800. Two
registers need to be read when the data format is a U32 value
(4 bytes); if both registers are not read, then a data value of 0
(zero) is returned. U32 values are in little endian format. The
maximum number of addresses that can be queried is 127
(0x7F) for each query message.
Tables 3 through 7 provide information on the function codes.
NOTE: All Query and Response cells below are 1 byte.
Number of
Addresses High
00
Data High Data Low
22
Preset Data Preset Data
High
00 04
Preset Data Preset Data
High
00 04
Table 15. Exception Codes.
Exception
Code Definition
01 Illegal
Function
02 Illegal
Data
Address
03 Illegal
Data
Value
33
Number of
Addresses Low CRC
01 A4
CRC
38 5D
Low CRC
B9 D1
Low CRC
B9 D1
Description
An illegal function as requested. Only
3, 4, 6 and 17 are supported.
Too many bytes requested, address
is out of range, register is read only,
or the number of address requested
is past the last register.
The "Preset Data" from function code
6 is invalid/out of range.
CRC
08
CRC
CRC
CRC
65-0090-6