Siemens S7-1200 - Page 590

Communication
10.5 S7 communication
S7-1200 Programmable controller
590 System Manual, 03/2014, A5E02486680-AG
On the rising edge of the REQ parameter, the read operation (GET) or write operation (PUT)
loads the ID, ADDR_1, and RD_1 (GET) or SD_1 (PUT) parameters.
● For GET: The remote CPU returns the requested data to the receive areas (RD_x),
starting with the next scan. When the read operation has completed without error, the
NDR parameter is set to 1. A new operation can only be started only after the previous
operation has completed.
● For PUT: The local CPU starts sending the data (SD_x) to the memory location (ADDR_x)
in the remote CPU. When the write operation has completed without error, the remote
CPU returns an execution acknowledgement. The DONE parameter of the PUT
instruction is then set to 1. A new write operation can only be started after the previous
operation has completed.
Note
To ensure data consistency, always evaluate when the operation has been completed
(NDR
= 1 for GET, or DONE = 1 for PUT) before accessing the data or initiating another
read or write operation.
The ERROR and STATUS parameters provide information about the status of the read
(GET) or write (PUT) operation.
Table 10- 38 Error information
ERROR
STATUS
(decimal)
Description
0 11
• New job cannot take effect since previous job is not yet completed.
• The job is now being processed in a priority class having lower priority.
0
25
Communication has started. The job is being processed.
1 1 Communications problems, such as:
• Connection description not loaded (local or remote)
• Connection interrupted (for example: cable, CPU is turned off, or CM/CB/CP is in
STOP mode)
• Connection to partner not yet established
1
2
Negative acknowledgement from the partner device. The task cannot be executed.
1 4 Errors in the send area pointers (RD_x for GET, or SD_x for PUT) involving the data
length or the data type.
1
8
Access error on the partner CPU
1 10 Access to the local user memory not possible (for example, attempting to access a
deleted DB)
1 12 When the SFB was called:
• An instance DB was specified that does not belong to GET or PUT
• No instance DB was specified, but rather a shared DB
• No instance DB found (loading a new instance DB)