Electerical Engineering, National University of Science & Technology
The design of an interface unit is described, in which RS232 serial data is converted to latched parallel data on 22 independent lines. The data direction of each line is programmable through the serial port. Two picocontrollers are employed in a parallel processing mode to give the required number of I/O pins, and data on the shared serial line is coded to separate data streams to the individual picocontrollers, and to avoid contention. The hardware configuration and the software for both the computer and microcontroller are described. The speed penalty of such a system compared with direct bus connection is analyzed.