SPI relay
The Apple IIe can run a SPI relay with the exact same card
design as the one described in doc/hw/z80/spi, which you can
then plug into one of the expansion slots. You only need to
perform these pin mappings:
Clock -> 7M
WR -> R/W
RD -> R/W going through a 40106 inverter.
IORQ -> DEVICE SELECT
D0:7 -> D0:7
A0:3 -> A0:3
A4:7 -> manual selection through jumpers
With such an adapter (or a card specifically for the IIe, but
with modified pin mappings), you can use the Z80 SPI relay in
the same way as if you were on a RC2014. Instead of PC! and PC@,
you read and write to the proper address. For example, if you
select clot 3, then SPI_CTL is going to be $c0b5 and SPI_DATA is
going to be $c0b4.
You have to be mindful of the power draw from your data lines,
however. The IIe is a bit picky on that front. For example, my
own prototype, to simplify my messy wiring, had IORQ go through
a diode and happily hop on the "big '138 line". It worked on the
RC2014, but on the IIe, the machine wouldn't because (I suspect)
too much power was drawn on the DEVICE SELECT line. Be removing
the diode and rewiring adequately, the problem was fixed.
This page generated at 2024-11-24 21:05:03 from documentation in CollapseOS snapshot 20230427.