MSaarna at 23:48, 7 November 2015

2015-11-07T23:48:29Z

MSaarna: Created page with "==Detection Code for POKEY in different locations== The following code (taken from 7800Basic, and originally adapted from [http://atariage.com/forums/topic/146725-detecting-p..."

2015-11-07T23:02:09Z

Created page with "==Detection Code for POKEY in different locations== The following code (taken from 7800Basic, and originally adapted from [http://atariage.com/forums/topic/146725-detecting-p..."

New page

==Detection Code for POKEY in different locations==

The following code (taken from 7800Basic, and originally adapted from [http://atariage.com/forums/topic/146725-detecting-pokey/ GroovyBee's POKEY detection routine]) checks both common POKEY locations ($450, and $4000) for the presence of a POKEY chip.

The code requires a pair of zero page locations (pokeybaselo and pokeybasehi) and another location (pokeydetected). If a POKEY chip is found, pokeydetected=0 and (pokeybaselo) will point at the POKEY memory location, through which you can access the POKEY registers indirectly.

<pre>
; Pokey register relative locations, since its base may be different
; depending on the hardware.
PAUDF0 = $0 ; extra audio channels and frequencies
PAUDC0 = $1
PAUDF1 = $2
PAUDC1 = $3
PAUDF2 = $4
PAUDC2 = $5
PAUDF3 = $6
PAUDC3 = $7
PAUDCTL = $8 ; Audio Control
PRANDOM = $A ; 17 bit polycounter pseudo random
PSKCTL = $F ; Serial Port control

detectpokeylocation
;XBoard/XM...
lda #%00010000
sta $470 ; tell XCTRL to enable the POKEY
ldx #1
detectpokeyloop
lda POKEYCHECKLO,x
sta pokeybaselo
lda POKEYCHECKHI,x
sta pokeybasehi
jsr checkforpokey
lda pokeydetected
beq foundpokeychip
dex
bpl detectpokeyloop
foundpokeychip
sta pokeydetected
rts

POKEYCHECKLO
.byte <$4000, <$0450
POKEYCHECKHI
.byte >$4000, >$0450

checkforpokey
ldy #$0f
lda #$00
sta pokeydetected
resetpokeyregistersloop
sta (pokeybase),y
dey
bpl resetpokeyregistersloop

ldy #PAUDCTL
sta (pokeybase),y
ldy #PSKCTL
sta (pokeybase),y

; let the dust settle...
nop
nop
nop

; we're in reset, so the RANDOM register should read $ff...
ldy #PRANDOM
lda (pokeybase),y
cmp #$ff
bne nopokeydetected

; take pokey out of reset...
ldy #PSKCTL
lda #3
sta (pokeybase),y
ldy #PAUDCTL
lda #0
sta (pokeybase),y

; let the dust settle again...
nop
nop
nop

; we're out of reset, so RANDOM should read non-$ff...
ldy #PRANDOM
lda (pokeybase),y
cmp #$ff
beq checkpokeyoncemore ;one $ff might be a fluke. try again...
rts

checkpokeyoncemore
lda (pokeybase),y
cmp #$ff
beq nopokeydetected
rts

nopokeydetected
dec pokeydetected
rts

</pre>

@@ Line 3: / Line 3: @@
 The following code (taken from 7800Basic, and originally adapted from [http://atariage.com/forums/topic/146725-detecting-pokey/ GroovyBee's POKEY detection routine]) checks both common POKEY locations ($450, and $4000) for the presence of a POKEY chip.
-The code requires a pair of zero page locations (pokeybaselo and pokeybasehi) and another location (pokeydetected). If a POKEY chip is found, pokeydetected=0 and (pokeybaselo) will point at the POKEY memory location, through which you can access the POKEY registers indirectly.
+The code requires a pair of zero page locations (pokeybaselo and pokeybasehi) and another location (pokeydetected). If a POKEY chip is found, pokeydetected=0 and (pokeybaselo) will point at the POKEY memory location, through which you can access the POKEY registers indirectly. The POKEY will be left in an initialized ready-to-use state.
 <pre>

Detecting POKEY - Revision history

MSaarna at 23:48, 7 November 2015

MSaarna: Created page with "==Detection Code for POKEY in different locations== The following code (taken from 7800Basic, and originally adapted from [http://atariage.com/forums/topic/146725-detecting-p..."