HP71 memory config observations

[Christoph Giesselink]

Hi Hans,

configuring a single-chip 64KB RAM was just a try in Emu71 v1.08 to see whats happen. First I was wondering about the address #20000 and even more that Emu71 was still working.

The primary goal was to check the memory mapping emulation of Emu71, especially the case of multiple modules configured at the same address. The MMU emulation of Emu71 v1.08 and earlier more or less base on my experiences with the bus arbitration of the Clarke and Yorke chips used in the latest generations of "Saturn CPU" calculators. The actual tests showed, that the real HP71 behave different to my expected results und so that the memory mapping emulation in Emu71 v1.08 is wrong in some cases.

Quote:what's going to happen if you try to read a card with the card reader? will that card overwrite the 0x2C000 window?

I don't have a card reader so I can't verfiy this. But first I don't know if the card reader or FRAM71 are soft or hard configured. In the case of hard configured memory mapped I/O I expect that such a module has a higher priority than any other soft configured module at the same address. But for the case, such a module in the Port5 slot is soft configured, I expect that any other module located at 0x2C000 will have a higher access priority.