Siemens SIMATIC S7-1200 - Page 1174

Communication processor and Modbus TCP
13.5 Modbus communication
S7-1200 Programmable controller
1174 System Manual, V4.2, 09/2016, A5E02486680-AK
MB_MOD
E
Modbus function
Data length
Operation and data
MB_DATA_ADDR
2 16 1 to 123 Write one or more holding registers:
1 to 123 words per request
40001 to 49999 or
400001 to 465535
116 16 1 to 123 Write one or more holding registers:
1 to 123 words per request
00000 to 65535
11 11 0 Read the server communication status word and
event counter. The status word indicates busy (0
= not busy, 0xFFFF = busy). The event counter
is incremented for each successful completion of
a message.
Both the MB_DATA_ADDR and MB_DATA_LEN
parameters of MB_CLIENT are ignored for this
function.
80 08 1
Check server status with diagnostic code 0x0000
(Loopback test, server echoes the request)
1 word per request
81 08 1 Reset server event counter with diagnostic code
0x000A
1 word per request
3 to 10,
12 to 79,
82 to 100,
107 to
114,
117 to 255
Reserved
Note
MB_DATA_PTR assigns a buffer to store data read/written to/from a Modbus TCP server
The data buffer can be located in a non
-optimized global DB or M memory address.
For a buffer in M memory, use the Any Pointer format. This is in the format P#"Bit Address"
"Data Type" "Length", an example would be P#M1000.0 WORD 500.