I have some SLC 5/03's and micrologix's on a DH485 network. One of the 5/03 is the 'master', it initiates most of the communications, using MSG reads and writes to the other nodes. Three questions:
1. The 5/03 has four MSG buffers, so it can handle four active MSG instructions at a time. If I use a sequencer or timer or use the DN and ER bits to enable only one MSG at a time, isn't performance taking a hit because I have only one MSG active at a time (wouldn't I get faster throughput with four active at a time)? I'm not concerned with scan time.
2. One node is down because of hardware problems. I use the DN and ER bits to toggle between the read and write MSG commands to this node. However, the EN, ER, and TO bits are all set for both the read and write commands, and since the DN and ER bits are used to toggle the MSG command, both are enabled at the same time. It seems the false to true transition of the MSG command is not resetting the ER bit, otherwise I should be seeing the bits toggle between each MSG command as each becomes active and then fails on timeout. I also ran into this when the entire network went down because of a cable break. When reconnected, the S:9 bits all turned on when the nodes became active again, but the MSG commands were all frozen and would not restart. I had to force the EN bits off to get things going again. Aside from the question 'why did they all freeze?', is there a way to condition the MSG commands to avoid this happening again? As I said, I condition them all with the DN and ER bits, so the read and writes should alternate.
3. Regarding the S:33/7 bit, the RSLogix help files and the online documentation contradict each other, one says that all MSG commands are processed when the bit is off and the other says that all MSG commands are processed when the bit is on. Which is it?
1. The 5/03 has four MSG buffers, so it can handle four active MSG instructions at a time. If I use a sequencer or timer or use the DN and ER bits to enable only one MSG at a time, isn't performance taking a hit because I have only one MSG active at a time (wouldn't I get faster throughput with four active at a time)? I'm not concerned with scan time.
2. One node is down because of hardware problems. I use the DN and ER bits to toggle between the read and write MSG commands to this node. However, the EN, ER, and TO bits are all set for both the read and write commands, and since the DN and ER bits are used to toggle the MSG command, both are enabled at the same time. It seems the false to true transition of the MSG command is not resetting the ER bit, otherwise I should be seeing the bits toggle between each MSG command as each becomes active and then fails on timeout. I also ran into this when the entire network went down because of a cable break. When reconnected, the S:9 bits all turned on when the nodes became active again, but the MSG commands were all frozen and would not restart. I had to force the EN bits off to get things going again. Aside from the question 'why did they all freeze?', is there a way to condition the MSG commands to avoid this happening again? As I said, I condition them all with the DN and ER bits, so the read and writes should alternate.
3. Regarding the S:33/7 bit, the RSLogix help files and the online documentation contradict each other, one says that all MSG commands are processed when the bit is off and the other says that all MSG commands are processed when the bit is on. Which is it?
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