penguin86/pato-z80-home-computer
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Perfected timings

Browse Source
This commit is contained in:
Daniele Verducci su MatissePenguin 2021-02-14 18:29:24 +01:00
parent 7e3896848f
commit d71e5b65cf
1 changed files with 11 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
pat80-io-devices/composite-pal-adapter/software/avr-assembly/video_generator.asm
View File

@ -32,7 +32,7 @@
.equ TIMER_DELAY_60US = 65535 - 1409 ; 719 cycles @ 24Mhz (minus overhead)
.equ TIMER_DELAY_30US = 65535 - 690 ; 719 cycles @ 24Mhz (minus overhead)
.equ TIMER_DELAY_2US = 65535 - 17 ; 48 cycles @ 24Mhz (minus overhead)
.equ TIMER_DELAY_4US = 65535 - 65 ; 96 cycles @ 24Mhz (minus overhead)
.equ TIMER_DELAY_4US = 65535 - 64 ; 96 cycles @ 24Mhz (minus overhead)
.equ BACK_PORCH_DELAY = 234 ; 186 cycles back porch + 48 cycles to leave 2 chunks empty (image padding)
@ -43,8 +43,8 @@ on_tim1_ovf:
sbi PORTD, BUSY_PIN
; called by timer 1 two times per line (every 32 uS) during hsync, unless drawing picture.
inc STATUS
; if STATUS >= 83 then STATUS=0
cpi STATUS, 85 ; TODO: Added a seventh sync pulse at end of screen because at the first short sync after the image, the timer doesn't tick at the right time
; if STATUS >= 176 then STATUS=0
cpi STATUS, 178 ; TODO: Added a seventh sync pulse at end of screen because at the first short sync after the image, the timer doesn't tick at the right time
brlo switch_status
clr STATUS
; check status and decide what to do
@ -53,13 +53,12 @@ on_tim1_ovf:
brlo long_sync ; 0-9: long sync
cpi STATUS, 20
brlo short_sync ; 10-19: short sync
cpi STATUS, 45
brlo empty_line ; 20-45: empty lines
cpi STATUS, 45
breq start_draw_picture ; 20: draw picture
cpi STATUS, 71
brlo empty_line ; 46-70 = draw empty lines
jmp short_sync ; 71-82 = short sync
cpi STATUS, 92
brlo empty_line ; 20-91: empty lines
breq start_draw_picture ; 92: draw picture
cpi STATUS, 164
brlo empty_line ; 93-165 = draw empty lines
jmp short_sync ; 166-177 = short sync
; reti is at end of all previous jumps
start_draw_picture:
@ -1360,10 +1359,10 @@ draw_line:
lsr A ; 1 cycle
out VIDEO_PORT_OUT, A ; 1 cycle
; chunk 47, 48, 49 (blank)
; blank right margin
clr A ; 1 cycle
out VIDEO_PORT_OUT, A ; 1 cycle
ldi VG_HIGH_ACCUM, 31 ; 1 cycle
ldi VG_HIGH_ACCUM, 28 ; 1 cycle
eol_porch_loop: ; requires 3 cpu cycles
dec VG_HIGH_ACCUM ; 1 cycle
brne eol_porch_loop ; 2 if jumps, 1 if continues