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Re: First thought on an interface (to use Paleolithic DROM)
Posted: Sun Jul 20, 2025 7:37 pm
by BigDumbDinosaur
I gloat!
Success has crowned my very efforts!
(bonus points if you can identify the source of those quotes without recourse to a search engine 
)
I vaguely remember seeing that phrase on a site associated with (or perhaps fixated with) Nixie tubes. No idea, though, as to who posted it.
Re: First thought on an interface (to use Paleolithic DROM)
Posted: Sun Jul 20, 2025 7:50 pm
by barnacle
If nixie, it's quite likely it was posted by me
And probably the other one, too.
It's from Gilbert and Sullivan's Iolanthe.
Neil
Re: First thought on an interface (to use Paleolithic DROM)
Posted: Mon Jul 21, 2025 2:33 pm
by barnacle
Running code on the board, entered using the keypad. A simple timer (runs slightly fast but it's just loop counting). It turns out that the code takes ~914us for each refresh cycle, so it counts 1094 ticks between each second update. This is just a simple 'something you can enter' code; a later version will use the 6522 to talk to the IRQ both to provide a constant LED/keypad update and provide a regular system tick, but I can't do that until I've soldered some diodes on Paleolithic as otherwise it trashes the LED patterns.
Code: Select all
; routines and addresses from vbios
ffd2 = convert equ $ffd2
9800 = led_addr equ $9800
00f6 = leds equ $f6
0446 = maxtick equ 1094 ; time measured with oscilloscope!
bss
0000 = org $0
0000 = ticks ds 2
0002 = secs ds 1
0003 = mins ds 1
0004 = hours ds 1
code
0200 = org $200
; initialise the processor
0200 : f8 sed ; we want decimal mode
0201 : a2ff ldx #$ff
0203 : 9a txs
; clear the blank LEDs
0204 : 64f8 stz leds+2
0206 : 64fb stz leds+5
0208 : 6402 stz secs
020a : 6403 stz mins
020c : 6404 stz hours
020e : reset:
020e : a946 lda # lo maxtick
0210 : 8500 sta ticks
0212 : a904 lda # hi maxtick
0214 : 8501 sta ticks+1
0216 : main:
0216 : a007 ldy #7 ; the counter
0218 : loop:
0218 : b9f600 lda leds,y ; read the current LED pattern
021b : 990098 sta led_addr,y ; put it in the current LED
021e : a200 ldx #0 ; now starting on the left
0220 : a504 lda hours
0222 : 20d2ff jsr convert ; place the hours
0225 : e8 inx ; skip the space
0226 : a503 lda mins
0228 : 20d2ff jsr convert ; place the minutes
022b : e8 inx ; skip the space
022c : a502 lda secs
022e : 20d2ff jsr convert ; and place the seconds
0231 : 88 dey
0232 : 10e4 bpl loop ; until all LEDs drawn
; now count the ticks
0234 : c600 dec ticks
0236 : d0de bne main
0238 : c601 dec ticks+1
023a : 10da bpl main ; we haven't got to a second yet
023c : 18 clc ; but now we have
023d : a502 lda secs
023f : 6901 adc #1
0241 : 8502 sta secs
0243 : c960 cmp #$60 ; we're adding in decimal mode!
0245 : d0c7 bne reset ; not 60, then back
0247 : a900 lda #0
0249 : 8502 sta secs ; else reset the seconds
024b : 18 clc
024c : a503 lda mins
024e : 6901 adc #1
0250 : 8503 sta mins
0252 : c960 cmp #$60 ; and the same for minutes
0254 : d0b8 bne reset
0256 : a900 lda #0
0258 : 8503 sta mins
025a : 18 clc
025b : a504 lda hours
025d : 6901 adc #1
025f : 8504 sta hours
0261 : c924 cmp #$24 ; and hours
0263 : d0a9 bne reset
0265 : a900 lda #0 ; else finally reset hours
0267 : 8504 sta hours
0269 : 80a3 bra reset
Neil
edit: corrected loop timing