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315-5195: unclear when the M68K can read register data #16

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jotego opened this issue Jul 28, 2022 · 1 comment
Open

315-5195: unclear when the M68K can read register data #16

jotego opened this issue Jul 28, 2022 · 1 comment

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@jotego
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jotego commented Jul 28, 2022

It looks like signal W31 will enable register writting. But it is not clear when the register data can be read by the M68K. It looks like registers 1 and 0 can be read (and 0xd 0xe during test) but what triggers that read? Is it W31 paired with the CPU read signal?
@furrtek
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furrtek commented Aug 2, 2022 •
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I believe that the M68K can't read anything from the 315-5195, it can only write to registers at startup. The direction signal for the M68K data pins seems to only be controlled by the r/w operation system, which means that only a MCU write operation would make the pins become outputs. I can't see any path that would allow the M68K itself to do that.
Only the MCU seems to have data read access (see "MCU READ" sheet).

(W31 was renamed to /REGS_SPACE).

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@jotego @furrtek