Read performance hint for SLC-5/Micrologix 1400

Hello all,
currently I’m migrating a SCADA to Igntion and I have to communicate with SLC-5/Micrologix 1400 PLCs. I have little experience with these PLCs, so I wonder if, performance wise, it is the same to read an Int/DInt, (HmiBool1 or B3:0, for example) and then create memory tags for the boolean values using an expression like getBit(HmiBool1, 0) or it is better to read the bit directly using the notation HmiBool1.0 or B3:0.0 on the tag path.

To write boolean values, I think I will use the direct bit access, in order to write to a tag and make the audit easier to read.

Any advice?


The driver will optimize reading multiple adjacent items, so just use the booleans. You definitely want to write to defined booleans, so the driver can intelligently use read-modify-write requests to perform those updates atomically. To maximize performance, try to keep data that Ignition will be subscribing in a few densely occupied data files, rather than spread across many files.

Thank you pturmel, very informative as always