We have a module that reads/writes to an AB SLC using the Ethernet port. But only the first 7 registers. The software is written in C to run under VxWorks (looks like Linux from the point of view of socket I/O) it will only read/write the first 7 registers in the AB PLC. Any ideas why?

Robert Cheetham
Sr. Software Engineer
Tuboscope

 

Packet length?

Regards
cww

 

Considering that AB doesn't publically post how to talk to the SLC5/05 by Ethernet I am guessing that you are reverse engineering the CSP packets being used and don't have full details.

My first guess is that you are correctly setting only 1 of 2 length fields. The main header has a length of attached data - attached data being another header and the command. Some of these "another headers" will have another length field. If you goofed on the 2nd header lengths it could be truncating the data.

best regards
- LynnL, www.digi.com