1. you need just nine. cd4017 (better its TTL counter part) + 9 i/o pins, one to pulse the decade counter and 8 to scan coulums. decade counter drives and port seneses.

2.you can also use a ls138 and 8 line multiplexer job will be done in just 7 i/os. but time taken in scanning will be more.

am i right?.


abhishek