Re: ROM Dump of Amiga Keyboard controller

From: Gerrit Heitsch <>
Date: Wed, 02 Jul 2014 17:08:01 +0200
Message-ID: <>
On 07/02/2014 04:06 PM, David Wood wrote:
> Considering the minimum clock rate, it's entirely possible to stall the
> clock long enough to get from 0v to 10v on /reset before a clock cycle
> completes.
> By the way, these NOP loops are getting pretty long, would it make sense
> to use a JMP at the end of the loop to avoid having the internal address
> bus loop into onboard device or ram locations?

The NOPs are just for the beginning so we get everything into a defined 
state no matter what gets interrupted when RESET goes to +10V. They can 
probably be shortened. Also, I think we can dispense with the 3 byte BIT 
command and just use the zero page version together with a NOP for 
syncing up. But for the moment we should leave it in place since it 
doesn't hurt.

And this is only a bit of test code. Once we figure out what is wrong 
and get it to run, all it does is set PORT D to $55 and then uses one of 
the killer opcodes to stop the CPU so PORT D remains stable. Once this 
runs reliably, we can think about the ROM dump code to load into RAM and 
how to start it.


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Received on 2014-07-02 17:00:02

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