name: HT6571 function: Multiple RS-232 Drivers and Receivers package: DIP20,20 manufacturer: Holtek +--()--+ VDD | 1 20| VCC RA1 | 2 19| RY1 RA2 | 3 18| RY2 RA3 | 4 17| RY3 DY1 | 5 16| DA1 DY2 | 6 15| DA2 RA4 | 7 14| RY4 DYY3 | 8 13| DA3 RA5 | 9 12| RY5 VSS |10 11| GND +------+ This pinout came from the Chipdir: http://www.chipdir.org/