An I/O pin uses one channel. Up to eight boards can be used in one system for a maximum of 256 pins (each board containing 32 I/O pins).
I/O Pin Block Diagram
The figure above is a simplified block diagram of a single I/O pin. This diagram shows how a single channel functions. Output data is stored in the output memory and is outputted from the board as a function of the CLK signal through an output buffer when enabled. In the other direction, the channel value is latched by the Strobe signal into the input buffer and stored in the input memory.
The direction of the I/O pins (input/output) depends on the output Control State. In addition, each output (driver) defined pin is also an input (receiver). The software can ignore the received data; however, its value in the input memory will be the same as the output value.