How to Assign Unique R_ID Values to Multiple PCS 7 Snd_AnaVal and Rcv_AnaVal Pairs
Yes. In PCS 7 V9.1 SP1, additional Snd_AnaVal/Rcv_AnaVal transfers can use the same configured S7 connection when each sender/receiver pair has its own unique R_ID and both blocks in a pair use the same value. The documentation reviewed does not establish a universal maximum number of pairs for the stated redundant CPU 410-5H arrangement, so confirm capacity against the exact CPU, communication load and installed block version.
Table of Contents
- Applies to PCS 7 V9.1 SP1
- How ID and R_ID identify a transfer
- Configure another analog-value pair
- Do not assume an unlimited block count
- Configure and verify the data exchange
- Communication load and payload limits
- Verification
- Limitations and Operational Precautions
- Engineer FAQ
- Technical References
- Related Articles
- Related Tags
Applies to PCS 7 V9.1 SP1
The question concerns two redundant CPU 410-5H systems exchanging analog values through the PCS 7 Advanced Process Library blocks Snd_AnaVal and Rcv_AnaVal, with the reported project on PCS 7 V9.1 SP1. Siemens' PCS 7 Industry Library V9.1 manual documents that the S7 communication ID comes from the configured connection and that R_ID identifies a matching send/receive pair. Confirm that the installed APL version and the specific CPU/connection configuration match before applying the examples.
How ID and R_ID identify a transfer
Treat ID as the configured S7 connection reference at that station and R_ID as the identifier that matches one sending block with its receiving block. For each transfer, use the same R_ID at the sender and its corresponding receiver. Give each additional transfer over that connection a different R_ID so the block pair remains uniquely identifiable. In a redundant system, the local ID values may refer to the connection configuration on each respective CPU; follow that project's NetPro configuration rather than copying one CPU's ID blindly.
Configure another analog-value pair
For the arrangement in the question, the existing logical transfers pair AS01 Snd_AnaVal R_ID 1 with the corresponding AS02 Rcv_AnaVal R_ID 1, and AS02 Snd_AnaVal R_ID 2 with AS01 Rcv_AnaVal R_ID 2. To add a second transfer in each direction, assign fresh R_ID values, such as 3 and 4, and use each value unchanged at both ends of its own transfer. Keep the configured connection ID appropriate to each station's S7 connection. The example values are illustrative; first verify uniqueness throughout the project and correct correspondence between each sender and receiver.
Do not assume an unlimited block count
The source response confirms multiple Snd_AnaVal/Rcv_AnaVal pairs can share a connection when they use different R_ID values, but it does not establish a numeric maximum. Siemens' V9.1 SP1 Industry Library manual describes the identifier relationship and block behavior; the material reviewed does not specify a universal maximum pair count for this CPU/configuration. Determine the practical limit from the applicable CPU communication resources, block documentation, configured communication load, and project validation for the exact hardware and cycle requirements.
Configure and verify the data exchange
- Check the S7 connection configuration and retain the correct local connection ID for each CPU. 2. List every intended analog transfer as a sender/receiver pair. 3. Assign a distinct R_ID to each pair and enter the same value at its sender and receiver. 4. Confirm that each receiver corresponds to the intended sender and that no other block pair reuses the same connection/R_ID combination. 5. Compile the CFC charts and resolve reported configuration errors. 6. Commission with representative values and verify that each receiver updates with the intended sender's values and status. Use a controlled test window before loading changes to a running system.
Communication load and payload limits
The ticket cites a 65,534-byte limit and default/maximum communication-load percentages, but these numerical claims were not confirmed in the applicable PCS 7 V9.1 SP1 APL reference reviewed here; they are omitted as general limits. CPU communication load and data capacity depend on the actual CPU, firmware, communication setup and block implementation. Check the CPU's version-specific data sheet and STEP 7/PCS 7 online help before setting limits or scaling the number and size of transfers.
Verification
Inspect the configured sender/receiver pair list, confirm matching R_ID values at both ends, and verify live values at each intended receive block under normal operation. Exercise communication fault behavior only through an approved commissioning test and confirm the configured substitute/status behavior for the installed APL block version. Compilation success alone does not prove that values are paired with the intended receiver.
Limitations and Operational Precautions
This guidance applies to the ticket's stated PCS 7 V9.1 SP1 context and APL communication blocks; it does not establish compatibility with other APL releases, CPU firmware, or connection types. The source does not identify the precise CPU firmware or provide a tested maximum count. Plan CPU communication load and validate configuration changes in a test or approved commissioning window. Do not download changes to a production CPU without the site's backup, authorization and rollback procedures.
Engineer FAQ
For every additional transfer, use a separate R_ID and set the same value on the matching sender and receiver. The reviewed release-specific manual does not establish a universal maximum number of pairs, so capacity must be confirmed against the configured CPU, communication load and applicable documentation.
Technical References
- Siemens, PCS 7 Industry Library for S7 V9.1, Function Manual, communication-block sections: https://support.industry.siemens.com/cs/attachments/109805918/S7IL91b_en-US.pdf (official document; search-indexed text reviewed, direct browser retrieval returned HTTP 403).
- Siemens, S7 Communication between S7-1500 and S7-300, application description, BSEND/BRCV background: https://support.industry.siemens.com/cs/attachments/18516182/18516182_S7_communication_S7-1500_S7-300_en.pdf (general S7 communication reference; not a PCS 7 APL sizing reference; direct retrieval returned HTTP 403).