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Apple2: implement get_tv()

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get_tv() will return TV_NTSC or TV_PAL for any Apple II model
with a way of checking vblank. For Apple ][ and ][+ it will
return TV_OTHER and let the user figure it out in another way.
This commit is contained in:
Colin Leroy-Mira
2025-04-26 12:56:57 +02:00
committed by Oliver Schmidt
parent 96e8e89776
commit 2085646e57
5 changed files with 232 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
doc/apple2.sgml
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@@ -354,6 +354,7 @@ usage.
<item>allow_lowercase
<item>beep
<item>dir_entry_count
<item>get_tv
<item>get_ostype
<item>gmtime_dt
<item>mktime_dt

1
doc/apple2enh.sgml
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@@ -333,6 +333,7 @@ usage.
<item>_datetime
<item>beep
<item>dir_entry_count
<item>get_tv
<item>get_ostype
<item>gmtime_dt
<item>mktime_dt

39
doc/funcref.sgml
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@@ -98,6 +98,7 @@ function.
<item>allow_lowercase
<item><ref id="beep" name="beep">
<item><ref id="dir_entry_count" name="dir_entry_count">
<item><ref id="get_tv" name="get_tv">
<item><ref id="get_ostype" name="get_ostype">
<item><ref id="gmtime_dt" name="gmtime_dt">
<item><ref id="mktime_dt" name="mktime_dt">
@@ -111,6 +112,7 @@ function.
<item>_dos_type
<item><ref id="beep" name="beep">
<item><ref id="dir_entry_count" name="dir_entry_count">
<item><ref id="get_tv" name="get_tv">
<item><ref id="get_ostype" name="get_ostype">
<item><ref id="gmtime_dt" name="gmtime_dt">
<item><ref id="mktime_dt" name="mktime_dt">
@@ -140,7 +142,7 @@ function.
<!-- <item><ref id="_setcolor_low" name="_setcolor_low"> -->
<item><ref id="_sound" name="_sound">
<item><ref id="get_ostype" name="get_ostype">
<!-- <item><ref id="get_tv" name="get_tv"> -->
<item><ref id="get_tv" name="get_tv">
</itemize>
(incomplete)
@@ -227,7 +229,7 @@ function.
<!-- <item><ref id="cbm_readdir" name="cbm_readdir"> -->
<!-- <item><ref id="cbm_save" name="cbm_save"> -->
<!-- <item><ref id="cbm_write" name="cbm_write"> -->
<!-- <item><ref id="get_tv" name="get_tv"> -->
<item><ref id="get_tv" name="get_tv">
<item><ref id="kbrepeat" name="kbrepeat">
<item><ref id="waitvsync" name="waitvsync">
</itemize>
@@ -348,7 +350,7 @@ function.
<itemize>
<!-- <item><ref id="get_numbanks" name="get_numbanks"> -->
<item><ref id="get_ostype" name="get_ostype">
<!-- <item><ref id="get_tv" name="get_tv"> -->
<item><ref id="get_tv" name="get_tv">
<!-- <item><ref id="set_tv" name="set_tv"> -->
<!-- <item><ref id="vera_layer_enable" name="vera_layer_enable"> -->
<!-- <item><ref id="vera_sprites_enable" name="vera_sprites_enable"> -->
@@ -443,7 +445,7 @@ see also <tt>testcode/lib/em-test.c</tt> and <tt>samples/multidemo.c</tt>.
<sect1><tt/gamate.h/<label id="gamate.h"><p>
<itemize>
<!-- <item><ref id="get_tv" name="get_tv"> -->
<item><ref id="get_tv" name="get_tv">
<item><ref id="waitvsync" name="waitvsync">
</itemize>
@@ -550,7 +552,7 @@ see also <tt>testcode/lib/em-test.c</tt> and <tt>samples/multidemo.c</tt>.
<sect1><tt/nes.h/<label id="nes.h"><p>
<itemize>
<!-- <item><ref id="get_tv" name="get_tv"> -->
<item><ref id="get_tv" name="get_tv">
<item><ref id="waitvsync" name="waitvsync">
</itemize>
@@ -568,7 +570,7 @@ It does not declare any functions.
<sect1><tt/pce.h/<label id="pce.h"><p>
<itemize>
<!-- <item><ref id="get_tv" name="get_tv"> -->
<item><ref id="get_tv" name="get_tv">
<item><ref id="waitvsync" name="waitvsync">
</itemize>
@@ -4108,6 +4110,31 @@ be used in presence of a prototype.
</quote>
<sect1>get_tv<label id="get_tv"><p>
<quote>
<descrip>
<tag/Function/The function returns the system's vertical blank frequency.
<tag/Header/<tt/<ref id="apple2.h" name="apple2.h">,
<ref id="atari.h" name="atari.h">, <ref id="cbm.h" name="cbm.h">,
<ref id="cx16.h" name="cx16.h">, <ref id="gamate.h" name="gamate.h">,
<ref id="nes.h" name="nes.h">, <ref id="pce.h" name="pce.h">/
<tag/Declaration/<tt/unsigned char get_tv (void);/
<tag/Description/<tt/get_tv/ is machine dependent and does not exist for
all supported targets. If it exists, it returns a number that identifies the
frequency at which the screen vertical blank happens (either 50 or 60Hz),
if possible.
<tag/Notes/<itemize>
<item>The function does not exist on all platforms.
<item>Return TV_NTSC for 60Hz systems, TV_PAL for 50Hz systems, or
TV_OTHER if the scan frequency can not be determined.
</itemize>
<tag/Availability/cc65 (not all platforms)
<tag/Example/None.
</descrip>
</quote>
<sect1>get_ostype<label id="get_ostype"><p>
<quote>

8
include/apple2.h
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@@ -122,6 +122,11 @@
#define APPLE_IIGS1 0x81 /* Apple IIgs (ROM 1) */
#define APPLE_IIGS3 0x83 /* Apple IIgs (ROM 3) */
/* Return codes for get_tv() */
#define TV_NTSC 0
#define TV_PAL 1
#define TV_OTHER 2
extern unsigned char _dos_type;
/* Valid _dos_type values:
**
@@ -200,6 +205,9 @@ extern void a2_lo_tgi[];
void beep (void);
/* Beep beep. */
unsigned char get_tv (void);
/* Get the machine vblank frequency. Returns one of the TV_xxx codes. */
unsigned char get_ostype (void);
/* Get the machine type. Returns one of the APPLE_xxx codes. */

189
libsrc/apple2/get_tv.s Normal file
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@@ -0,0 +1,189 @@
;
; Colin Leroy-Mira <colin@colino.net>, 2025
;
; unsigned char __fastcall__ get_tv(void)
;
.export _get_tv
.import _set_iigs_speed, _get_iigs_speed
.import ostype
.constructor calibrate_tv, 2
.include "accelerator.inc"
.include "apple2.inc"
.include "get_tv.inc"
.segment "ONCE"
; Cycle wasters
waste_72:
jsr waste_36
waste_36:
jsr waste_12
waste_24:
jsr waste_12
waste_12:
rts
.proc calibrate_tv
lda ostype
bmi iigs
cmp #$20
bcc iip
cmp #$40
bcc iie
iic: jmp calibrate_iic
iigs: jmp calibrate_iigs
iie: jmp calibrate_iie
iip: rts ; Keep TV::OTHER.
.endproc
; Magic numbers
WASTE_LOOP_CYCLES = 92 ; The wait loop total cycles
NTSC_LOOP_COUNT = 17030/WASTE_LOOP_CYCLES ; How many loops expected on NTSC
PAL_LOOP_COUNT = 20280/WASTE_LOOP_CYCLES ; How many loops expected on PAL
STOP_PTRIG = 16500/WASTE_LOOP_CYCLES ; Stop PTRIG at 16.5ms
; Carry set at enter: wait for VBL +
; Carry clear at enter: wait for VBL -
; Increments X every 92 cycles.
.proc count_until_vbl_bit
lda #$10 ; BPL
bcc :+
lda #$30 ; BMI
: sta sign
; Wait for VBLsign change with 92 cycles loops.
; Hit PTRIG repeatedly so that accelerators will slow down.
; But stop hitting PTRIG after 16.5ms cycles, so that on the //c,
; the VBLINT will not be reset right before we get it. 16.5ms
; is a good value because it's far enough from 17ms for NTSC
; models, and close enough to 20.2ms for PAL models that accelerators
; will stay slow until there. (5ms usually).
: cpx #STOP_PTRIG ; 2 - see if we spent 16.5ms already
bcs notrig ; 4 / 5 - if so, stop hitting PTRIG
sta PTRIG ; 8 - otherwise hit it
bcc count ; 11
notrig:
nop ; 7 - keep cycle count constant when not
nop ; 9 - hitting PTRIG
nop ; 11
count:
inx ; 13
jsr waste_72 ; 85
bit RDVBLBAR ; 89 - Wait for VBL change
sign:
bpl :- ; 92 - patched with bpl/bmi
rts
.endproc
.proc calibrate_iic
php
sei
sta IOUDISOFF
lda RDVBLMSK
pha ; Back up for cleanup
bit ENVBL
bit PTRIG ; Reset VBL interrupt flag
: bit RDVBLBAR ; Wait for one VBL
bpl :-
bit PTRIG ; Reset VBL interrupt flag again
ldx #$00
clc
jsr count_until_vbl_bit
pla ; Cleanup
asl
bcs :+ ; VBL interrupts were already enabled
bit DISVBL
: sta IOUDISON ; IIc Tech Ref Man: The firmware normally leaves IOUDIS on.
plp
jmp calibrate_done
.endproc
.proc calibrate_iie
: bit RDVBLBAR ; Wait for bit 7 to be off (VBL start)
bmi :-
: bit RDVBLBAR ; Wait for bit 7 to be on (VBL end)
bpl :-
; Wait and count during a full cycle
ldx #$00
sec
jsr count_until_vbl_bit
clc
jsr count_until_vbl_bit
jmp calibrate_done
.endproc
.proc calibrate_iigs
; Backup speed and slow down
jsr _get_iigs_speed
pha
lda #SPEED_SLOW
jsr _set_iigs_speed
; The same as IIe, but reverted, because... something?
: bit RDVBLBAR ; Wait for bit 7 to be on (VBL start)
bpl :-
: bit RDVBLBAR ; Wait for bit 7 to be off (VBL end)
bmi :-
; Wait and count during a full cycle
ldx #$00
clc
jsr count_until_vbl_bit
sec
jsr count_until_vbl_bit
jsr calibrate_done
; Restore user speed
pla
jmp _set_iigs_speed
.endproc
.proc calibrate_done
; Consider X +/- 3 to be valid,
; anything else is unknown.
lda #TV::NTSC
cpx #NTSC_LOOP_COUNT-3
bcc unexpected
cpx #NTSC_LOOP_COUNT+3
bcc matched
lda #TV::PAL
cpx #PAL_LOOP_COUNT-3
bcc unexpected
cpx #PAL_LOOP_COUNT+3
bcs unexpected
matched:
sta tv
unexpected:
rts
.endproc
.code
; The only thing remaining from that code after init
.proc _get_tv
lda tv
ldx #>$0000
rts
.endproc
.segment "INIT"
tv: .byte TV::OTHER