IRPR

Conforms to BS 4421

Signals

SC/AC/SO/AO control signals can be inverted.

• D0-D7 (or D0-D15), 8/16 data wires with bidirectional transmission,
• DP0,DP1 signals for parity check
• SC source control (sender data is valid)
• AC acceptor control (receiver confirms receipt of data)
• SO source operable (sender is ready)
• AO acceptor operable (receiver is ready)

SO and AO signals are optional.

For two-way communication (typically SPU DPR or TNS APK cards), the control signals are supplemented with a direction designation (e.g. ACI, ACO, etc.). The SC (for receive) and AC (for ready to send) signals can be easily used to generate IRQs. In terms of implementation, control signals are usually fed to the flip-flop in the transmitter so that it is set by writing data, the output of the flip-flop is the SC signal, and the flip-flop is reset using the AC signal from the transmitter.

Wikipedia talks about bi-directional transmission defined by SO and AO states, I haven't seen this anywhere.

References

• https://cs.wikipedia.org/wiki/IRPR (WebArchive)