Re: [foxboro] FBM224 and ProSoft modules

On Thu, Jan 20, 2005 at 12:39:34PM -0500, Johnson, Alex (Foxboro) wrote:
> The FBM224 is a Modbus RTU Master.
> 
> Throughput varies with baud rate and turn around time in the PLC. Generally,
> that's where we see the performance hit. Seems most PLCs think they have
> more important things to do than respond to our requests.
> 
Can I assume a smiley there?

In any case, yes, my hope/expectations is that the limitation will be as
follows:
1. PLC processing (see later)
2. RS-232 wire speed.
3. FBM242 processing limits.

As opposed to Gateway 30's that work out something like this:

1. GW 30 CPU
2. wire speed
3. PLC

Now, the ProSoft module will communicate with the PLC data table via block
transfers, which in turn require ladder program support. Only 1 block
transfer can be performed per I/O scan, and each block transfer is limited
to 128 (8 bit) words. I expect that there will probably need to be a
BTW/BTR pair for each data exchange.

Given all the above, I would be very curios as to anyones experience in
prototyping this, or in an actual application.

BTW, I'm assuming that I will have access to all the CP60's block set for
processing data to/from the PLC in this method, is this correct? As opposed
to the somewhat limited block set that the integrator 30 supports.

Also does the ECB set up port assignments baud parity etc?

Thanks.

-- 
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
                                                -- Benjamin Franklin
 
 
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