Re: [stella] Why do we use the SEI instruction???

Subject: Re: [stella] Why do we use the SEI instruction???
From: "Eric Ball" <ericball@xxxxxxxxxxxx>
Date: Mon, 4 Aug 2003 11:28:49 -0400
>From an AtariAge post I did:

Although the 6507 doesn't have NMI or IRQ pins, it's good programming
practice to have those vectors point somewhere, either the same as RESET or
an RTI instruction. (And to include an SEI instruction in your
initialization section.) That way if the 6507 flakes out it won't crash

And Thomas's addendum:
Yes, but IRQ can also be triggered by BRK.

Some games (Parker Bros) even use BRK to call subroutines (I have explained
that on [stella], it's quite strange and definitely not for newbies).

And you can use BRK for debugging. E.g. you can check if a branch is always
taken by adding a BRK just behind it and point the IRQ vector to a special
routine or simply to the RESET address.

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