Protocol Limitations and FAQ
python-snap7 implements the classic S7 protocol over TCP/IP. The following
limitations apply to s7.Client:
Limitation |
Explanation |
|---|---|
Read tag/symbol names from PLC |
The classic S7 protocol only addresses data by area, DB number, and byte offset; callers must provide the addresses. |
Get DB structure or layout from PLC |
Classic S7 reads DBs as raw bytes, so callers must supply the layout. |
Discover PLCs on the network |
The classic S7 protocol has no broadcast discovery mechanism. However,
python-snap7 provides PROFINET DCP discovery via the |
Create PLC backups |
Full project backup requires TIA Portal. python-snap7 can upload individual blocks, but this is not a complete backup. |
Serial PPI has additional constraints: the current implementation supports one PC master and one S7-200 slave, not multimaster token passing or PPI over TCP. See S7-200 Serial PPI.