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 horribly. 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. ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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