Posted By
gerliczer
on 2016-05-08
03:11:40
|  Re: Switching off roms
Well, going by simple logic, as the +4 reports 60671 bytes available when turned on, it obviously has to have a mechanism to turn off ROMs. So, your basic question shouldn't have been asked. Take no offence, please.
As the [7|8]501 is a very-very close relative of the 6510|8500, the programming model is identical. Although our CPU has no NMI pin. Turning off the ROMs and taking full control is the standard procedure in demo code, and mostly with programs requiring more than 16kB of memory.
To do it, you have to perform an arbitrary write operation on the TED's $3F phantom register. To reverse it, you have to perform an arbitrary write operation on the TED's $3E phantom register. But this is usually written in the programming documentation. I'd recommend SVS's excellent Ultimate Map, which has many information organised in a handy Excel file.
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