This board fixes the I/O select problem on former boards, which did not qualify /IORQ with /M1 high. This extra qualification prevents the board from selecting on an INTA (Interrupt Acknowledge) cycle.
There was/is a Kicad issue where signals exiting a global bus did not connect to traces of the same name on the same sheet.
The schematic is correct but A7..A2 leaving the bus are not connected to A7..A2 on K1..K6.
The following changes are required - six link wires need to be added.
- A7: connect U5.2 to U2.3
- A6: connect U5.4 to U2.5
- A5: connect U5.6 to U2.7
- A4: connect U5.8 to U2.9
- A3: connect U5.11 to U2.12
- A2: connect U5.13 to U2.14
This is is corrected in the 171005 version.