Siemens S7-1200 System Manual page 750
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- Operating instructions manual (132 pages) ,
- Programming manualline (74 pages) ,
- Manual (46 pages)
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Communication processor and Modbus TCP
12.5 Modbus communication
Table 12- 68 Data types for the parameters
Parameter and type
REQ
IN
MB_ADDR
IN
MODE
IN
DATA_ADDR
IN
DATA_LEN
IN
DATA_PTR
IN
DONE
OUT
BUSY
OUT
ERROR
OUT
STATUS
OUT
750
Data type
Description
Bool
0=No request
1= Request to transmit data to Modbus slave
V1.0: USInt
Modbus RTU station address:
V2.0: UInt
Standard addressing range (1 to 247)
Extended addressing range (1 to 65535)
The value of 0 is reserved for broadcasting a message to all Modbus
slaves. Modbus function codes 05, 06, 15 and 16 are the only function
codes supported for broadcast.
USInt
Mode Selection: Specifies the type of request (read, write, or diagnostic).
See the Modbus functions table below for details.
UDInt
Starting Address in the slave: Specifies the starting address of the data to
be accessed in the Modbus slave. See the Modbus functions table below
for valid addresses.
UInt
Data Length: Specifies the number of bits or words to be accessed in this
request. See the Modbus functions table below for valid lengths.
Variant
Data Pointer: Points to the M or DB address (Standard DB type) for the
data being written or read.
Bool
The DONE bit is TRUE for one scan, after the last request was completed
with no error.
Bool
0 – No MB_MASTER operation in progress
•
1 – MB_MASTER operation in progress
•
Bool
The ERROR bit is TRUE for one scan, after the last request was
terminated with an error. The error code value at the STATUS parameter
is valid only during the single scan where ERROR = TRUE.
Word
Execution condition code
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
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