https://wikiti.brandonw.net/api.php?action=feedcontributions&feedformat=atom&user=144.131.13.168 2026-04-23T01:16:04Z User contributions MediaWiki 1.23.5 https://wikiti.brandonw.net/index.php?title=83Plus:OS:How_BCALLs_work 2005-09-10T04:10:55Z

<p>144.131.13.168: How BCALLs work</p> <hr /> <div>Sorry, this article isn't very well written. It would be good if someone else could maybe look at the TI-OS code a bit and explain this better.<br /> <br /> BCALLs are the way to call TI-OS ROM routines, and also the way that the branch table works in multi-page apps. A BCALL is the RST 28h instruction, with a 16-bit number after it which is used to identify which routine it is calling.<br /> <br /> If the first bit (bit 15) of the number is set, this is what the OS does:<br /> <br /> *It resets bit 15<br /> *It adds 0x4000 to the number<br /> *It maps page 1F into memory space 4000-7FFF<br /> <br /> Otherwise, if bit 15 is reset and bit 14 is set, this is what the OS does:<br /> <br /> *It resets bit 14<br /> *It adds 0x4000 to the number<br /> *It maps page 1B into memory space 4000-7FFF<br /> <br /> Otherwise, if bit 15 and 14 are both reset, it is treated as a multipage app branch, which is explained in the TI developer's guide.<br /> <br /> Once the OS has mapped the appropriate page into 4000-7FFF, it uses the number in memory as a pointer into this page. In page 1B and 1F there are lists of vectors for the actual ROM routines. The vectors are 3 bytes, the first two bytes are a memory address and the next byte is the page that the routine is on.</div>

144.131.13.168 https://wikiti.brandonw.net/index.php?title=83Plus:OS:How_BCALLs_work 2005-09-10T04:07:38Z

<p>144.131.13.168: </p> <hr /> <div>How BCALLS work.<br /> Sorry, this article isn't very well written. It would be good if someone else could maybe look at the TI-OS code a bit and explain this better.<br /> <br /> BCALLs are the way to call TI-OS ROM routines, and also the way that the branch table works in multi-page apps. A BCALL is the RST 28h instruction, with a 16-bit number after it which is used to identify which routine it is calling.<br /> <br /> If the first bit (bit 15) of the number is set, this is what the OS does:<br /> <br /> -It resets bit 15<br /> -It adds 0x4000 to the number<br /> -It maps page 1F into memory space 4000-7FFF<br /> <br /> Otherwise, if bit 15 is reset and bit 14 is set, this is what the OS does:<br /> <br /> -It resets bit 14<br /> -It adds 0x4000 to the number<br /> -It maps page 1B into memory space 4000-7FFF<br /> <br /> Otherwise, if bit 15 and 14 are both reset, it is treated as a multipage app branch, which is explained in the TI developer's guide.<br /> <br /> Once the OS has mapped the appropriate page into 4000-7FFF, it uses the number in memory as a pointer into this page. In page 1B and 1F there are lists of vectors for the actual ROM routines. The vectors are 3 bytes, the first two bytes are a memory address and the next byte is the page that the routine is on.</div>

144.131.13.168 https://wikiti.brandonw.net/index.php?title=83Plus:OS:ByROMPage 2005-09-10T03:51:10Z

<p>144.131.13.168: </p> <hr /> <div>[[Category:83:OS Information|ROM Page 1B]]<br /> {{stub}}<br /> <br /> This page contains at the start a list of 3-byte vectors for ROM calls.<br /> <br /> ==Structure==<br /> <br /> ''to do''</div>

144.131.13.168