parallel/serial converter - keyboard adapter

keyboard adapter Parallel/serial converters have a var- iety of applications in computer technology, for instance, in interface circuits for printers with a serial in- put, or as adapter for a keyboard with parallel output when the com- puter has one or more serial, but no more parallel, interfaces available. The circuit is based on four LSTTL ICs: a four-bit synchronous binary counter, IC1, a parallel-load eight-bit shift register, IC2, a quad two-input NAND gate, IC3, and a quad two- input NOR gate, IC4. As the circuit contains neither time-dependent nor discrete elements, you"ll have to take care of its control by the system yourself. In the quiescent state, the binary counter is set to 1010 (decimal 10). This condition is decoded by NAND gates N1 . . . N3 and NOR gate N7 into a stop signal for the counter (the output of N3 = ENABLE in- put — pin 10 — of IC1 = logic 0). The output of N3 is logic 1 for all other input combinations to N1 and N7. The shift register is inhibite...