Re: A86: User interrupt question
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Re: A86: User interrupt question
At 07:32 1998-04-04 -0500, you wrote:
>1. Can you have an interrupt durring and interrupt? Is this limit by the
>number of clock cycles in my interrupt?
Actually, that depends on WHAT interrupt you mean... the Z80 on the TI-86
only has one interrupt (INT), and then the answer is YES.
However, when an INT occurs, the IFF flags are cleared (= DI),
so unless you enable the interrupts (EI), no interrupt will interrupt
your current interrupt handler :-) As you may have noticed, the
interrupt handler at $38 ends with
EI
RETI
That EI is necessary.
Thus there is no way to know if you're "inside" an interrupt handler
or not - the status of the Z80 is the same as when you execute a DI
instruction.
>2. Can I use regular ROM calls in:
> 1. The user interrupt and all other user areas?
> 2. The interrupt using IM 2 and the 257 byte table?
Well, yes, but some routines are probably not so smart to call
if you intend to make a TSR program that is active in the TI-OS
(for instance, variable routines). The most important thing should
be to preserve the current pages at $4000-$7FFF and $8000-$BFFF.
--
Real name: Jimmy Mårdell
IRC......: Yarin
Email....: mailto:yarin@acc.umu.se <-- NEW E-MAIL ADDRESS!!!!
Homepage.: http://www.algonet.se/~mja/
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