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Memory is determined solely by BANK_ALTZP.
Previously, we just used whatever the segment was that got passed in. But aside from switching the stack and zero page, ALTZP also changes where bank-switchable memory is read from and written to; it's either always aux memory (ALTZP is on) or always main memory (ALTZP is off).
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@ -16,6 +16,12 @@ SEGMENT_READER(apple2_mem_read_bank)
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mach = (apple2 *)_mach;
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mach = (apple2 *)_mach;
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// In the case of bank-switchable memory, BANK_ALTZP is the ultimate
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// arbitrator; if it's on, we have to use aux, and if not, we have
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// to use main. Whatever the segment was that was passed in will
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// turn out to be immaterial.
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segment = (mach->bank_switch & BANK_ALTZP) ? mach->aux : mach->main;
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if (~mach->bank_switch & BANK_RAM) {
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if (~mach->bank_switch & BANK_RAM) {
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// We need to account for the difference in address location
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// We need to account for the difference in address location
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// before we can successfully get any data from ROM.
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// before we can successfully get any data from ROM.
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@ -52,6 +58,9 @@ SEGMENT_WRITER(apple2_mem_write_bank)
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return;
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return;
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}
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}
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// See my spiel in the read bank mapper; the same applies here.
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segment = (mach->bank_switch & BANK_ALTZP) ? mach->aux : mach->main;
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// You will note, if we've gotten here, that it's possible to write
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// You will note, if we've gotten here, that it's possible to write
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// to the bank-switch addresses even if the ROM flag is 1. It's
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// to the bank-switch addresses even if the ROM flag is 1. It's
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// true! Except that writes never go to ROM. That is to say, it's
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// true! Except that writes never go to ROM. That is to say, it's
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