Using The Function Blocks With The Rk 512 Computer Connection - Siemens Simatic S7-300 CP 341 User Manual

Communication via Function Blocks

6.4 Using the Function Blocks with the RK 512 Computer Connection

6.4 Using the Function Blocks with the RK 512 Computer Connection
The function blocks available for connection to a communication partner with the RK 512
procedure are as follows:
● FB 8 P_SND_RK for sending or fetching data
● FB 7 P_RCV_RK for receiving or providing data
Data transmission options
Active requests:
The FB 8 P_SND_RK function block enables you to issue active requests to the CP 341 in
the user program of the CPU. You can
● Send data from your automation system to a remote communication partner.
● Fetch data from a remote communication partner and store it in an S7 data area of your
automation system
Note: If you fetch data from a CP 341, you must always program an FB P_RCV_RK on
the CP 341.
Passive requests:
The FB 7 P_RCV_RK function block enables you to use passive requests to coordinate the
reading and providing of data on the CP 341. The communication partner is active. You can
● Read in data sent from the communication partner in an S7 data area of your automation
system.
● Provide data in your automation system to a remote communication partner.
Requests that can be processed simultaneously
Only one active and one passive request can be programmed for each CP 341 in the user
program. While the CP 341 is transacting an active request, it can simultaneously process a
passive request.
Bear in mind, too, that you can use only:
● 1 instance data block for FB P_SND_RK and
● 1 instance data block for FB P_RCV_RK
This is because the statuses needed for the FB's internal routines are stored in the instance
data block.
Interprocessor communication flag
The interprocessor communication flag functionality familiar from SIMATIC S5 is supported
as a means of coordinating asynchronous overwriting on receipt or provision of data
(FB 7 P_RCV_RK) by the CP 341 and the processing of data on the CPU. The
interprocessor communication flags can only be used with the RK 512 computer link.
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CP 341 Point-to-Point Communication, Installation and Parameter Assignment
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Manual, 09/2008, A5E02191071-01