Vic20 Startup sequence to main screen Display? (was: Help Cartridge with a startup SOUND)
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- audronic1
- Vic 20 Drifter
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Vic20 Startup sequence to main screen Display? (was: Help Cartridge with a startup SOUND)
Hi All
I am New to Denial.
I with to find a Game - Rom That Starts up with Music- Sounds Noises upon Power up ?
WHY:- Because I have a Vic20 that is unwell and I only have a thought that it may be running.
and if I can put a Cart that starts up with some sound then this might help
I have repaired a lot of other machines BUT this Vic 20 is still a challenge
Thanks
Keep Safe
Ray
I am New to Denial.
I with to find a Game - Rom That Starts up with Music- Sounds Noises upon Power up ?
WHY:- Because I have a Vic20 that is unwell and I only have a thought that it may be running.
and if I can put a Cart that starts up with some sound then this might help
I have repaired a lot of other machines BUT this Vic 20 is still a challenge
Thanks
Keep Safe
Ray
- audronic1
- Vic 20 Drifter
- Posts: 22
- Joined: Wed Jun 14, 2023 6:17 pm
- Location: Williamstown
- Occupation: Old Techo
Re: Vic20 Startup sequence to main screen Display?
Hi All
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
Keep Safe
Ray
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
Keep Safe
Ray
Re: Vic20 Startup sequence to main screen Display?
Welcome.
The VIC-20 boots up like this:
- 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 $C000
- audronic1
- Vic 20 Drifter
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Re: Vic20 Startup sequence to main screen Display?
@srowe
Thanks for that.
Is there a link to that sort of information that goes little further ?
Keep Safe
Ray
Thanks for that.
Is there a link to that sort of information that goes little further ?
Keep Safe
Ray
Re: Vic20 Startup sequence to main screen Display?
The best description in is the KERNAL disassembly
Code: Select all
14935 ;***********************************************************************************;
14936 ;
14937 ; RESET, hardware reset starts here
14938
14939 START
14940 LDX #$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
- Vic 20 Drifter
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Re: Vic20 Startup sequence to main screen Display?
@ srowe
Thanks
Vic20 Kernal ROM Info - eden.mose.org.uk
That will be good to have a look at.
Keep Safe
Ray
Thanks
Vic20 Kernal ROM Info - eden.mose.org.uk
That will be good to have a look at.
Keep Safe
Ray
- Mike
- Herr VC
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- Joined: Wed Dec 01, 2004 1:57 pm
- Location: Munich, Germany
- Occupation: electrical engineer
Re: Vic20 Startup sequence to main screen Display?
There's a slight lack of detail in your fault description, but then I think you are likely doing the fourth or fifth step of tests before the first when using a cartridge for checks.audronic1 wrote:I have an unwell Vic20 (later version) [...]
Does the Power LED turn on? Do you get (just) a black screen or something else? Have you checked the supply voltages on the mainboard with a multimeter? 5 VDC within range? 9 VAC within range? Ripple on the 5 VDC below, say, 0.1 V? You can check the latter by switching the multimeter to AC while probing the 5V supply rail. The video chip is known to cease video generation as soon as there's excessive ripple on the 5V. Do you get a proper Reset pulse on Pin 40 of the 6502? Does any of the chips get excessively hot after a short time? Etc. ...
- audronic1
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Re: Vic20 Startup sequence to main screen Display? (was: Help Cartridge with a startup SOUND)
Hi Mike
Various replies to your questions
Does the Power LED turn on?
:- Yes
Do you get (just) a black screen or something else?
:- Something else
See Photo
Have you checked the supply voltages on the mainboard with a multimeter? 5 VDC within range?
:- 4.93
9 VAC within range?
:- 10.8
Ripple on the 5 VDC below, say, 0.1 V?
:-0.9 Mv
Do you get a proper Reset pulse on Pin 40 of the 6502?
:- Yes tested about 2 Second Delay
Does any of the chips get excessively hot after a short time? Etc. ...
:- No all are OK
Some Photos below
Keep Safe
Ray
Various replies to your questions
Does the Power LED turn on?
:- Yes
Do you get (just) a black screen or something else?
:- Something else
See Photo
Have you checked the supply voltages on the mainboard with a multimeter? 5 VDC within range?
:- 4.93
9 VAC within range?
:- 10.8
Ripple on the 5 VDC below, say, 0.1 V?
:-0.9 Mv
Do you get a proper Reset pulse on Pin 40 of the 6502?
:- Yes tested about 2 Second Delay
Does any of the chips get excessively hot after a short time? Etc. ...
:- No all are OK
Some Photos below
Keep Safe
Ray
Re: Vic20 Startup sequence to main screen Display? (was: Help Cartridge with a startup SOUND)
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.
You could try poking to change the border color or start a sound to see if only the display seems affected.
Re: Vic20 Startup sequence to main screen Display? (was: Help Cartridge with a startup SOUND)
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
https://portcommodore.com/rcarlsen/cbm/vic20/vic20.txt
- audronic1
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Re: Vic20 Startup sequence to main screen Display? (was: Help Cartridge with a startup SOUND)
@srowesrowe 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
Thanks I will have a closer look at the UD1-UD8/UE9
and a reread of the Document By Ray Carlsen
Thanks
Keep Safe
Ray W
- audronic1
- Vic 20 Drifter
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Re: Vic20 Startup sequence to main screen Display? (was: Help Cartridge with a startup SOUND)
@bjontebjonte 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.
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
Thanks
Keep Safe
Ray W
Re: Vic20 Startup sequence to main screen Display? (was: Help Cartridge with a startup SOUND)
- audronic1
- Vic 20 Drifter
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- Joined: Wed Jun 14, 2023 6:17 pm
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Re: Vic20 Startup sequence to main screen Display? (was: Help Cartridge with a startup SOUND)
@bjontebjonte 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.
Keyboard does not show any change no matter what I press on the keyboard ( I also swapped the 6522s over no change.
I tested some Pokes :-
Poke 36878,15
Poke 36875,225
No Sound
Thanks for the thought
Keep Safe
Ray W
- audronic1
- Vic 20 Drifter
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- Joined: Wed Jun 14, 2023 6:17 pm
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Re: Vic20 Startup sequence to main screen Display? (was: Help Cartridge with a startup SOUND)
@srowe
The pokes did not work , also changed the 6522s over still no output.
Thanks
Keep Safe
Ray W