Abstract: Disclosed is a method and apparatus for interfacing N bit-serial communication channels to an N-bit parallel communication channel. The serial channels are interfaced simultaneously, i.e., during a single bit time, with the parallel channel by an interface unit that is shared by the serial channels. The interface unit is microprocessor based. To service all serial channels simultaneously, the microprocessor's interface program divides each bit interval into 2N time slots and allocates two time slots per bit interval to each of the N channels, one time slot for functions associted with receipt of bits from the serial channel and transmittal thereof on the parallel channel, and one time slot for functions associated with receipt of data from the parallel channel and transmittal thereof on the serial channel.