Bidirectional Serial Parallel Converter

10 by R. Baltissen This interface circuit enables doing rather more than nor- mally possible with the com- puter"s serial (RS232) port. Serial output data from the computer is converted into parallel for- mat, and parallel data applied to the interface is converted into a serial bit stream for reception by the computer. The interface is based on the industry standard UART (univer- sal asynchronous receiver/ transmitter) Type AY-5-1013, or the CMOS version of it, the CDP1854 from RCA. Serial data from the computer is received at input RXD, and inverted in T1 for driving the RSI input on the UART, which converts the received word into 8-bit parallel format (RDo-RD7). The shifting in of serial bits is clocked by the 19,200 Hz signal applied to the RCP and TCP input. This fixes the baud rate of the interface at 1200 (19,200/16). The baud rate generator is a conventional design based on a binary counter/divider with built-in clock oscillator, which is crystal controlled here and operat...