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Corrects second range, explains 'only implicitly' on C800–CFFF.

Thomas Harte 2020-11-25 12:54:43 -05:00
parent 0ebf1469e5
commit 2538136507
1 changed files with 2 additions and 2 deletions
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Apple-IIe-Memory-Paging.md

@ -4,7 +4,7 @@ Apple provides multiple overlapping paging mechanisms which in total divide an A
## 0000–01FF ## 0000–01FF
Reading and writing: contains auxiliary RAM if `ALTZP` is set. Contains base RAM otherwise. Reading and writing: contains auxiliary RAM if `ALTZP` is set. Contains base RAM otherwise.
## 0300–03FF; 0800–1FFF; 4000–BFFF ## 0200–03FF; 0800–1FFF; 4000–BFFF
Reading: contains base RAM if `RAMRD` is reset; contains auxiliary RAM otherwise. Reading: contains base RAM if `RAMRD` is reset; contains auxiliary RAM otherwise.
Writing: as per reading, but regarding `RAMWRT` rather than `RAMRD`. Writing: as per reading, but regarding `RAMWRT` rather than `RAMRD`.
@ -31,7 +31,7 @@ Contains ROM if `RDCXROM` is set or `SLOTC3ROM` is reset. Otherwise is unmapped,
## C800–CFFF ## C800–CFFF
Contains ROM if `RDCXROM` or `RDC8ROM` is set. Otherwise is unmapped, allowing cards to respond. Contains ROM if `RDCXROM` or `RDC8ROM` is set. Otherwise is unmapped, allowing cards to respond.
`RDC8ROM` is documented only implicitly; it is set by any access within the C3 page while `SLOTC3ROM` is reset. It is reset by an access to `CFFF`, or by system reset. `RDC8ROM` is documented only implicitly; it is set by any access within the C3 page while `SLOTC3ROM` is reset. It is reset by an access to `CFFF`, or by system reset. This adheres to the standard contract with cards for this space: any card may claim this area upon an access to its ROM but must release it upon an access to `CFFF`.
## D000–DFFF ## D000–DFFF
Reading: contains ROM if the language card `read` flip flop is *disabled*. Contains base RAM if the flip flop is enabled and `ALTZP` is reset. Otherwise contains auxiliary RAM. Reading: contains ROM if the language card `read` flip flop is *disabled*. Contains base RAM if the flip flop is enabled and `ALTZP` is reset. Otherwise contains auxiliary RAM.