Denial

audronic1 wrote: ↑Wed Jun 14, 2023 6:55 pm New User here.

Is their a document using simple terms the Vic20 Startup sequence to main screen Display ?

I have an unwell Vic20 (later version) FAB no. 251040-01, Assy No 250403, Revision D, 1982

and a startup sequence MAY help

• on reset the 6502 jumps to the vector at $FFFC
• the initial KERNAL routine looks for an autostart signature at $A004 and jumps to the vector at $A000 if a cartridge is present in BLK5
• otherwise it checks for the amount of RAM, on error it goes into a tight loop
• more initialization follows, VIAs, VIC
• finally, the KERNAL jumps to the BASIC vector in $C000

audronic1 wrote: ↑Thu Jun 15, 2023 4:10 am Thanks for that.
Is there a link to that sort of information that goes little further ?

14935 ;***********************************************************************************;
14936 ;
14937 ; RESET, hardware reset starts here
14938 
14939 START
14940         LDX     #$FF                    ; set .X for stack
14941         SEI                             ; disable interrupts
14942         TXS                             ; clear stack
14943         CLD                             ; clear decimal mode
14944         JSR     CHKAUTO                 ; scan for autostart ROM at $A000
14945         BNE     LAB_FD2F                ; if not there continue VIC startup
14946 
14947         JMP     (XROMCOLD)              ; call ROM start code
14948 
14949 LAB_FD2F
14950         JSR     INITMEM                 ; initialise and test RAM
14951         JSR     FRESTOR                 ; restore default I/O vectors
14952         JSR     INITVIA                 ; initialise I/O registers
14953         JSR     INITSK                  ; initialise hardware
14954         CLI                             ; enable interrupts
14955         JMP     (COLDST)                ; execute BASIC

audronic1 wrote:I have an unwell Vic20 (later version) [...]

srowe wrote: ↑Sun Jun 18, 2023 12:20 am You seem to have socketed pretty much everything, from the screen I would say there's a fault in the address buffering between the VIC and the CPU. That would suggest UD1 and/or UD8/UE8.

https://portcommodore.com/rcarlsen/cbm/vic20/vic20.txt

bjonte wrote: ↑Sat Jun 17, 2023 10:10 pm You seem to get as far as the VIC chip initialization since you have something displayed with the correct number of volumns and rows. If you type on the keyboard, does the screen change in any way as a response?

You could try poking to change the border color or start a sound to see if only the display seems affected.

audronic1 wrote: ↑Sun Jun 18, 2023 6:32 am I will connect a keyboard.
as I am New to Vic 20's I don't know of any pokes yet
If you can help with the pokes that would be appreciated

POKE36878,15
POKE36875,200

bjonte wrote: ↑Sat Jun 17, 2023 10:10 pm You seem to get as far as the VIC chip initialization since you have something displayed with the correct number of volumns and rows. If you type on the keyboard, does the screen change in any way as a response?

You could try poking to change the border color or start a sound to see if only the display seems affected.

srowe wrote: ↑Sun Jun 18, 2023 6:34 am

audronic1 wrote: ↑Sun Jun 18, 2023 6:32 am I will connect a keyboard.
as I am New to Vic 20's I don't know of any pokes yet
If you can help with the pokes that would be appreciated

Try just

Code: Select all

POKE36878,15
POKE36875,200