THE ZX-ATKEY CIRCUIT 5V 5V 5V ZX81 PCB REAR ZX/ASCII ROM | | | AT KBD EDGE CONNECTOR 27C256 1M PICAXE18X 4.7K 4.7K PLUG ______________ | 0.1 _________ | | +5V ---> 5V | /CE |20-+-||--13|OUT7 | | | DATA D0 -----------11| D0 A8 |25--------6|OUT0 IN7|16-+---|--------o D1 -----------12| D1 A9 |24--------7|OUT1 IN6|15_ | 0V-o o-5V D2 -----------13| D2 A10 |21--------8|OUT2 | `---+------o o D3 -----------15| D3 A11 |23--------9|OUT3 | CLOCK D4 -----------16| D4 A12 |2--------10|OUT4 | A8 -----------10| A0 A13 |26-------11|OUT5 | A9 ------------9| A1 A14 |27-------12|OUT6 | A10 ------------8| A2 | | | A11 ------------7| A3 D5 |17-------17|IN0 | A12 ------------6| A4 D6 |18-------18|IN1 | A13 ------------5| A5 D7 |19--------3|IN2 | A14 ------------4| A6 | | SOUT|2--180---- SERIAL OUT A15 ------------3| A7 | 5V | SIN|3--22K--+- SERIAL IN A0 -->|--+----22| /OE Vdd|28---|---14|Vdd | | 1N4448 | | Vpp|1____| | RESET|4 __ 10K RD -->|--+ |_____Vss______| | |___Vss___| | | | |14 | |5 | 0V IORQ -->|--+---[4.7K]----| === 0.1 | | 0V GND __________________|_____________|__________| | RST _______________________________________________________|