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This Apple DA: Fix RAMWorks bank detection/counting. Fixes #131

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This commit is contained in:
Joshua Bell 2019-02-28 19:38:31 -08:00
parent 6edb9a3e22
commit 41cf8f5452
1 changed files with 30 additions and 5 deletions
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35
desk.acc/this.apple.s
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@ -1182,13 +1182,19 @@ fail: clc
;;; ============================================================
;;; Calculate RamWorks memory; returns number of banks in Y
;;; (256 banks = 0, since there must be at least 1)
;;;
;;; Note the bus floats for RamWorks RAM when the bank has no RAM,
;;; or bank selection may wrap to an earlier bank.
;;; or bank selection may wrap to an earlier bank. This requires
;;; three passes (mark, count, restore); if count and restore are
;;; combined, it will produce false-positives if wrapping occurs
;;; (see https://github.com/inexorabletash/a2d/issues/131).
;;;
;;; RamWorks-style cards are not guaranteed to have contiguous banks.
;;; a user can install 64Kb or 256Kb chips in a physical bank, in the
;;; former case, a gap in banks will appear. Additionally, the piggy
;;; back cards may not have contiguous banks depending on capacity
;;; and installed chips.
;;;
;;; AE RamWorks cards can only support 8M max (banks $00-$7F), but
;;; the various emulators support 16M max (banks $00-$FF).
;;;
@ -1214,8 +1220,11 @@ fail: clc
;; Assumes ALTZPON on entry/exit
RWBANK := $C073
ldy #0 ; populated bank count
;; Iterate downwards (in case unpopulated banks wrap to earlier ones),
;; saving bytes and marking each bank.
.scope
ldx #255 ; bank we are checking
: stx RWBANK
copy sigb0, buf0,x ; preserve bytes
@ -1227,10 +1236,11 @@ fail: clc
dex
cpx #255
bne :-
.endscope
;; Iterate upwards, tallying and restoring valid banks.
;; Iterate upwards, tallying valid banks.
.scope
ldx #0 ; bank we are checking
ldy #0 ; populated bank count
loop: stx RWBANK ; select bank
txa
cmp sigb0 ; verify first signature
@ -1238,11 +1248,26 @@ loop: stx RWBANK ; select bank
eor #$FF
cmp sigb1 ; verify second signature
bne next
iny ; match - count it, and restore
copy buf0,x, sigb0
iny ; match - count it
next: inx ; next bank
bne loop ; if we hit 256 banks, make sure we exit
.endscope
;; Iterate upwards, restoring valid banks.
.scope
ldx #0 ; bank we are checking
loop: stx RWBANK ; select bank
txa
cmp sigb0 ; verify first signature
bne next
eor #$FF
cmp sigb1 ; verify second signature
bne next
copy buf0,x, sigb0 ; match - restore it
copy buf1,x, sigb1
next: inx ; next bank
bne loop ; if we hit 256 banks, make sure we exit
.endscope
;; Switch back to RW bank 0 (normal aux memory)
lda #0