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peasant: update some more seek comments

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This commit is contained in:
Vince Weaver 2022-01-13 19:34:28 -05:00
parent 840db1ba72
commit 0d0a9ff956
1 changed files with 11 additions and 10 deletions
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21
games/peasant/qboot_stage2.s
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@ -264,33 +264,34 @@ curtrk_smc:
lda #0 ; current track
sta tmpval_smc+1 ; save current track for later
; calculate how far we need to seek
; calculate direction to seek
sec
phase_smc:
sbc #$d1 ; track*2 to seek to
beq seekret ; if equal, we are already there
; so we are done
; A is distance, update direction
bcs seeking_out ; if positive, skip ahead
bcs seeking_out ; if positive, seeking out to 34
seeking_in:
eor #$ff ; negate the distance
eor #$ff ; negate the result? (why?)
inc curtrk_smc+1 ; move track counter inward
bcc ssback ; bra
seeking_out:
adc #$fe ; distance -=1 (carry always 1)
adc #$fe ; difference -=1 (carry always 1)
dec curtrk_smc+1 ; move track counter outward
ssback:
cmp step_smc+1 ; compare to step
bcc skip_set_step ; if below minimum, don't change?
;==================
; step the proper number of times
;================================
; step the proper length of time
; taking into account momentum?
step_smc:
lda #$d1 ; load step value
@ -309,7 +310,7 @@ skip_set_step:
bcs skip11
tay ; acceleration value in Y
tay ; acceleration offset in Y
do_phase_on:
sec ; carry set is phase on
@ -328,9 +329,9 @@ do_phase_common:
stx sector_smc+1
; A is the track?
and #3 ; mask to 1 of 4 phases
rol ; double for index (put C in bit 1)
rol ; double to the 8 phase on/off
; with carry the on/off
tax
slotpatch8:
sta $c0d1, X ; flip the phase
; C080...C087 seeks inward (toward 34)