[A83] Re: Ti-83+ jump

To: assembly-83@lists.ticalc.org
Subject: [A83] Re: Ti-83+ jump
From: "Adriaan Coosemans" <adriaanc@mail.com>
Date: Sun, 11 Nov 2001 15:46:57 +0100
Reply-To: assembly-83@lists.ticalc.org


When you execute an assembly program on the TI83-, the TIOS switches to rom page 0Ch (in 4000h-7FFFh), which is actually a jump table to the proper routines. The location of the routines might change over different rom
version, but page 0Ch remains the same. Calling 4709h will always do the same on every rom version.

On the 83+(SE) this is not possible, because apps need to use rom calls too and you can't have both an app page and some other rom page (with a jump table) loaded at the same time. And so TI invented the bcall/bjump. A bcall is a call to a routine which remembers the current page loaded. Then it loads a page similar to the jump table on the 83-. There it finds the proper address off a specific routine. When that romcall returns the bcall routine switches the original rom page back and gives control back to the asm program or flash app.

Note that bcalls/bjumps are only for rom calls and not for calls within an asm program or flash app.

Tijl Coosemans

> From: "The one and only SUCKER ..." <sucker_pvn@hotmail.com>
>
> Why do we need to do a bjump/bcall with a ti-83+ (and SE?)??
> Isn't there a way to just do a jp/jr or a call xxxx??
>
> SUCKER
>
-- 

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