I'm converting an obsolete MTL8000 multiplexor to DeltaV remote I/O (M-series). The cards are almost entirely discrete inputs (motor run statuses / "M" contact).
The existing modules were designed with "external references" to DI blocks that brought in the MTL8000 I/O via RS485 / Modbus RTU. The only DST was the the serial "datasets" which brought in the discrete I/O as one "read" of the Modbus registers.
To simplify the cutover, I want to just use the DST in place of the external reference to the DI block. We're aiming to do one rack of eight cards in a day while the plant is running. The new I/O is connected to the DeltaV system so we can commission the RIO processors and assign the appropriate DST to each channel.
Am I correct to presume that the DST value will be a "1" or a "0" just like the external reference to the DI block (which pointed to the modbus register). The original design did not do any signal conditioning or alarming in the DI block . . . I think the original systems engineer thought he needed them (the DI blocks) to pass the Modbus I/O to DeltaV modules. Who knows maybe you did in version 4.
I was thinking I could just bulk edit the modules and change the external references to point to the DST (both INPUT_1 and INPUT_2 pointing to the same DST) for the corresponding RIO channel. Note this is how some of us achieved a measure of redundancy for serial I/O before there was actual hardware redundancy . . .
If you have any caveats or suggestions I would welcome them.
-John
Andre Dicaire
In reply to Andre Dicaire: