Re: 6502 stack register at reset

From: didier derny <*didier_at_aida.org*> Date: Sat, 25 Nov 2017 21:56:07 +0100 Message-ID: <a9f7e4b1-e815-a49a-27d5-d8a5f7e920a8@aida.org> · didier_at_aida.org

the problem occurred on a replica 1 (original apple  1 monitor)

I checked the monitor code no initialization of the stack

my code was working fine on commodore and on a sym 1


On 25/11/2017 21:34, silverdr@wfmh.org.pl wrote:
>> On 2017-11-25, at 20:59, Gerrit Heitsch <gerrit@laosinh.s.bawue.de> wrote:
>>
>> On 11/25/2017 08:50 PM, didier derny wrote:
>>> Is there any 6502 starting with an initialized stack register at reset ?
>>> a few month ago I was struggling with a strange bug...
>>> the program was crashing or working randomly
>>> I discovered that the machine had a stack register never initialized
>> As far as I know, the RESET squence on about every 6502 system contains the following 2 commands:
>>
>> LDX #$FF
>> TXS
>>
>> to make sure the stack pointer contains the proper value.
> Yup - I even remember wondering why.. long time ago. That's until I read somewhere that the SP is not initialised on H/W reset.
>


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