7800 SERIES S7800A KEYBOARD DISPLAY MODULE
33
65-009
0-6
Excep
tion
Code Definition Desc
rip
t
ion
01 Illegal
Function
An illegal function as requested. Only
3, 4, 6 and 17 are supported.
02
Illegal
Data
Address
Too many bytes requested, address
is out of range, register is read only,
or the number of address requested
is past the last register.
03 Illegal
Data
Value
The "Preset Data" from function code
6 is invalid/out of range.
APPENDIX C: MODBUS DATA FEATURES
See Appendix A page 25 for Setup.
OPERATION
The S7800 ModBus
TM
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
ModBus
TM
registers.
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.
Table 9. Query Message Format for Function Codes 3 and
4.
Slave Address
Function
Code
Start
ing
Address
High
Start
ing
Address
Low
Number
of
Addresses
High
Number
of
Addresses
Low
CRC CRC
01 03 00 0A 00 01 A4 08
Table 10. Response Message Format for Function Codes 3 and
4.
Slave Address Function Code Byte Count Data High Data Low CRC CRC
01 03 02 00 22 38 5D
Table 11. Query Message Format for Function Code 6 (Broadcast is supported by using a slave address of 0
0).
Slave
A
dd
ress
Function
Co
de
Start
ing
Address
High
Start
ing
Address
Low
Preset Data
High
Preset Data
Low
CRC CRC
01 06 00 7F 00 04 B9 D1
Table 12. Response Message Format for Function Code 6 (There is no response if the query was
b
roadcas
t.)
Slave
A
dd
ress
Function
Co
de
Start
ing
Address
High
Start
ing
Address
Low
Preset Data
High
Preset Data
Low
CRC CRC
01 06 00 7F 00 04 B9 D1
Table 13. Query Message Format for Function Code 17.
Slave
A
dd
ress
Function
Co
de
CRC
CRC
03 11 C1 4C
NOTE: See Table 18 for function code 17 response forma
t.
Table 14. Exception Response Message
Fo
rma
t.
Table 15. Exception Codes.
Slave
Address
Function
Code
80h
Exception
Code
CRC CRC
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