Can we use parallel port on the slave in RCM4000?

For information on the slave port, see the Rabbit 4000 processor manual:

The data input registers are written by the master (the external device) and are read by the
processor. The data output registers are written by the processor and are read by the master.
Note that the data registers are named from the point of view of the processor. The slave
device can only read the data input registers and write to the data output registers. Similarly,
the master device can only read the data input registers and write the data output registers.
Both devices can read and write to the status register.