Direct Hardware Control - SeaLevel PLC-16.PCI User Manual

Direct Hardware Control

In systems where the user's program has direct access to the hardware (i.e. DOS) the
table below gives the mapping and functions that the PLC-16.PCI provides.
Function Available Port Address Hex
RD = Read, RD/WR = Read or Write
Reading the Inputs
The inputs are active Low. If no voltage is applied across one of the differential
inputs it returns a binary one (1) on that bit. If an AC or DC voltage is applied it
returns a binary zero (0) on that bit.
Writing the Outputs
The output ports are the only ports that can be written. The relays on a standard
PLC-16.PCI are normally open. To close a relay a binary one (1) must be written to
the appropriate bit.
Reading the Outputs
The relay ports can also be read to determine the status of the various relays. A read
will return the ones complement (or opposite) of the value that is currently written to
the port.
© Sealevel Systems, Inc.
RD A
B
RD/WR C
D
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Port Type
Base+0 Input Port (Opto Input)
Base+1 Not Assigned
Base+2 Output Port (Reed Relays)
Base+3 Not Assigned
PLC-16.PCI User Manual