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Re: Steal RAM -- Question
- Subject: Re: Steal RAM -- Question
- From: "David Wilson" <mcs6502@gmail.com>
- Date: 6 Nov 2006 01:43:18 -0800
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Bryan Parkoff wrote:
> We know that 16KB RAM has even switch on $C08X to set zero to WRTCOUNT
> (PREWRITE) and odd switch on $C08X to add 1 or 2 to WRTCOUNT. If WRTCOUNT
> is set to 2 then HIGH RAM for writing is enabled. My question is why do odd
> switch on $C08X set zero to WRTCOUNT if STA instruction (Write Only) is used
> unlikely to disable HIGH RAM for writing. Only even switch on $C08X is used
> to disable HIGH RAM for writing. Please explain what STA instruction is
> used for?
According to Jim Sather, the Language card was designed to be
compatible with the DOS routines (called by the INT and FP commands)
used to access the Firmware card. See "Understanding the Apple II"
pages 5-28 to 5-31.