On 21/04/2022 16:20, Mike Jagdis via Sdcc-user wrote:
Start within the 0x3ff..0x1ff region and the stack
wraps around. Start outside that and... well... you can have... fun...?
I found the following article in which the author finds through some
experimentation that - at least for the STM8S103 - if the stack pointer
is manually initialised to a value outside the 0x1FF-0x3FF area, then
push/pop will decrement/increment perfectly happily. However, when the
register value wraps around at 0x0, it is not to ram end, but to 0xFFFF.
https://sudonull.com/post/13801-Break-STM8-stack
I mean, I guess it's not surprising seeing as RM0016 talks in section
3.1.2 about the possibility to implement a custom stack model outside
the normal area, which wouldn't be possible if the above behaviour
didn't occur.
I_think_ the non-rollover parts just let you do your own thing (maybe
there's still a comparator that triggers an overflow event though?)
Maybe when RM0016 says "The stack roll-over limit is not implemented on
all devices", they actually mean that "a limit does not exist", rather
than "a limit exists, but does not automatically roll over". Because, I
guess, thinking about it, what would be the point of the latter?
Regards,
Basil Hussain
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