83Plus:OS:ByROMPage

From WikiTI
Revision as of 11:39, 13 September 2005 by Gambit (Talk | contribs)

Jump to: navigation, search


This page contains at the start a list of 3-byte vectors for ROM calls. This is then used by the B_CALL routine to determine what address on what page each ROM call resides. This is page 1B for the TI-83 Plus, 3B for the TI-84 Plus and 7B for the TI-83 Plus Silver Edition & the TI-84 Plus Silver Edition.

Structure

Each 3-byte vector contains an address and a page number. The address comes first, stored in little-endian format, followed by the page number.

Example Vector Table
Address Common Name LSB Addr. Ptr. MSB Addr. Ptr. Page Number
4000 JErrorNo C7 25 00
4003 FontHook A3 77 7B
4006 LocalizeHook 44 77 7B

Note: The preceding values were obtained from TI-OS v1.15. Values on other OSs are most likely to differ.


In this manner, TI can change the address pointer and page of the actual routine on a different OS version (e.g. they needed to update a section of code) and the B_CALL routine would still point to the correct page and address.

See Also