Moved here as it's a separate issue. Mark
Dave . . . I have a similar, outstanding, issue associated with empty sideways bank detection (especially cartridge sockets!) with the AP6. Jonathan has had to add several NOPs, after writing to a sideways bank, before reading back. Sometimes this isn't enough (certain combinations of Elk/Plus 1). So, I was thinking . . . The common element is the Plus 1 - would it make sense to add a pull-up resistor to, probably, just one of the data lines in the Plus 1. If Jonathan can advise what data he uses for socket detection and then choose a line to pull-up that would fix both issues!hoglet wrote:I think the root cause of this confusion is that when no serial port is present, a read of &FC65 returns &FC (i.e. the high byte of the address) due to data bus capacitance. This is sufficient to make the +1 ROM think there has been a a serial interrupt.
p.s. I (or users) could carry out this mode when fitting the AP6. And I could add a description of the mod to the AP5 User Guide.