Parallel ASCII keyboards

On 7/27/06, Ethan Dicks <ethan.dicks at gmail.com> wrote: AIM 65 USER'S GUIDE 7.2.8 Keyboard Interface The interface to the AIM 65 keyboard is through the R6532 RIOT (see Figure 7-10). Z33 R6532 peripheral I/O lines PA0 through PA7 are assigned to keyboard input lines KI1 through KI8, respectively. R6532 lines PB0 through PB7 are wired to the keyboard output lines KO1 through KO8, respec- tively. When scanning for key depression, a logic 0 is placed in the R6532 Output Register A (ORA) in one bit posi- tion at a time corresponding to one KI line. The logic 0 provides a low output to the KI line key switches. Each key depressed of the switches connected to selected KI line will present a closed circuit output from KO1-KO8 causing a logic 0 to be present in the respective bit position of R6532 Output Register B (ORB). Each unpressed key presents an open input circuit to PB0-PB7 causing a logic 1 to be present in the respective R6532 ORB bit position.