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Common I/O options


Most I/O modules use a common syntax for mapping physical I/O points to MAT points. In addition, each I/O module may have additional configuration.


The mapping between the physical I/O and the plc points is specified using the "map" table. The format of each line is
map [inv | invert] {in | out} <io_addr> <matplc point>
inv or invert
invert the value being read from/writen to physical IO All the bits are inverted, which is handy for physical I/O that uses negative logic (on = 0, off = 1) - whether it's simply a wrongly wired switch, or a sensor that's only available N/C where previously it was N/O.

copy the state of the physical Input/Output to the matplc point (it is an input)

copy the state of the matplc point to the physical Output (it is an output)

address of physical input/output. The acceptable format this address will depend on the type physical I/O we will be interfacing with. Each different MatPLC I/O module accepts a different io_addr format.

<matplc point>
the MAT point to which this physical input/output is to be mapped.


For instance, suppose that we are using the parallel port I/O module. We have leds that will light up when the output is low, so we choose to invert all the outputs so the leds will light up when the plc point is set to 1.

According to the Parallel port section, D.x is the acceptable format for the parallel port I/O module. D specifies the D register, and x the bit of that register.

The mapping table might look something like this:

map inv out D.0 L1
map inv out D.1 L2
map inv out D.2 L3
map inv out D.3 L4


$Date: 2004/12/28 05:32:11 $