OPNDRN Primitive

The OPNDRN primitive is similar to a TRI primitive, with a single input and a single output. An OPNDRN primitive fed by a signal called my_signal is equivalent to a TRI primitive whose output enable input is fed by the complement of my_signal, and whose primary input is fed by a GND primitive.

If the input to the OPNDRN primitive is low, the output will be low. If the input is high, the output will be a high-impedance logic level.

When you use an OPNDRN buffer, you must observe the following rules in addition to the rules listed in Primitive/Port Interconnections:

• An OPNDRN buffer may drive only one BIDIR. You must use a BIDIR pin if feedback is included after the OPNDRN buffer.
• If an OPNDRN buffer feeds logic, it must also feed a BIDIR pin. If it feeds a BIDIR pin, it may not feed any other outputs.