Why would you change a master address?

jabramson

I inherited a NI4100 and upon playing around with it, I noticed that the master address had been changed from 5001 to 5003. My question is, Why? I know some devices use 5002 for control, but this is just a basic NI-4100 unit. I can't envision a scenario where 5001 would be in use more than once on the same system ID.

Unfortunately, the code was already wiped prior to me getting it, so I couldn't dig through that for ideas.

Thanks.

GregG

Some people like to keep their master device numbers all unique across systems. It's not necessary, but I've seen it done. So system 1's master uses 5001:X:1 then system 2's devices get changed to 5002:X:2 etc. Personally I always refer to them by name, so the actual numbers are irrelevant other than when looking at the online device trees.

chill

I really can't think of a single reason to do that. I've seen it done too, but there's no good reason under ordinary circumstances.
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John Nagy

First, it's not the "master's address" but the IO device set address you are discussing. It's a separate entity in the same box as the CPU, or "master"... which usually is set to address 0, SYSTEM 1.

I can think of several reasons to change the device ports address from the default 5001 to 5003. One might be that they were using some NXI processors as slaves on ICSNet, and one used to be the master... so they are still addressed as 5001 and 5002. Wired on ICSNet, they can't have the same address on the AXLINK buss.

Same goes for a card frame that may have already been using the 5001 space before the 4100 arrived.

Or just that's what someone arbitrarily chose when writing the code, and it is easier to conform the address than rewrite the code.

The default address is just that, where they park it to start. They let you change it, so people do.
When I started with our company years ago, they had their own standards and readdressed the "5001" device to "2000" and the Master System Number to "1000" in every system for no clear reason. While it certainly worked, there was no advantage to the make-work of changing it... so we eventually standardized on the "standard" numbers.

jjames

One nice thing is that the new NX masters do not allow you to change it and will always be 5001.

Perhaps a sign as to what we think it should be?