Re: Hardware emulation of 6509 using 6502?

From: Michał Pleban <lists_at_michau.name>
Date: Sun, 04 Mar 2018 14:16:09 +0100
Message-ID: <5A9BF199.70207@michau.name>
Hello!

Jim Brain wrote:

> My unit also fails on the last 3 tests (direct 1 succeeds).

It might be interesting to see what values you are getting in these tests?

> If I try Mia's suggestion to direct the bank to 0xf during reads of
> $0/$1, the ram test fails.  

That is strange and rather unexpected. Can you post test results in this
case too?

> If I use $e, the ram test succeeds, and indirect 1 then works.  

That makes sense - there is no read from RAM in this case, so you are
reading back only the value from the latch. That supports the theory
that the problems are contention between read from the latch and the RAM.

> Direct and Indirect 2 always fail.

These tests are meant to test whether the read back returns only lowest
4 bits, i.e. if you write $FF, the real 6509 will read back $0F. You
might want to check your Verilog for that behaviour.

Regards,
Michau.




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