83Plus:OS:How BCALLs work - Revision history

Dr. D'nar: 84+CSE

2013-05-04T07:06:51Z

84+CSE

Dr. D'nar: Added speed information. It belongs SOMEWHERE.

2009-06-27T20:20:16Z

Added speed information. It belongs SOMEWHERE.

Burntfuse: Cleaned up the wording a bit

2006-09-01T21:51:48Z

Cleaned up the wording a bit

Dan Englender: link to page1b info

2006-04-09T20:01:28Z

link to page1b info

84plusfreak: Added category

2005-09-10T09:05:36Z

Added category

84plusfreak: Added page numbers for 84+ & SE

2005-09-10T09:03:36Z

Added page numbers for 84+ & SE

144.131.13.168: How BCALLs work

2005-09-10T04:10:55Z

How BCALLs work

144.131.13.168 at 04:07, 10 September 2005

2005-09-10T04:07:38Z

New page

How BCALLS work.
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.

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.

If the first bit (bit 15) of the number is set, this is what the OS does:

-It resets bit 15
-It adds 0x4000 to the number
-It maps page 1F into memory space 4000-7FFF

Otherwise, if bit 15 is reset and bit 14 is set, this is what the OS does:

-It resets bit 14
-It adds 0x4000 to the number
-It maps page 1B into memory space 4000-7FFF

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.

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.

@@ Line 8: / Line 8: @@
 *It resets bit 15
 *It adds 0x4000 to the number
-*It maps page 1F/3F/7F* into memory space 4000-7FFF
+*It maps page 1F/3F/7F/FF* into memory space 4000-7FFF
 Otherwise, if bit 15 is reset and bit 14 is set, this is what the OS does:
@@ Line 14: / Line 14: @@
 *It resets bit 14
 *It adds 0x4000 to the number
-*It maps page 1B/3B/7B** into memory space 4000-7FFF
+*It maps page 1B/3B/7B/05** into memory space 4000-7FFF
 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.
@@ Line 20: / Line 20: @@
 Once the OS has mapped the appropriate page into 4000-7FFF, it uses the number as a pointer to a vector on this page. On pages 1B and 1F there are lists of vectors for the actual ROM routines. Each vector is 3 bytes - the first two bytes are a memory address and the third byte is the page that the routine is on.
-<nowiki>*1F for the TI-83 Plus, 3F for the TI-84 Plus and 7F for the TI-83 Plus Silver Edition & the TI-84 Plus Silver Edition.</nowiki><br>
+<nowiki>*1F for the TI-83 Plus, 3F for the TI-84 Plus, 7F for the TI-83 Plus Silver Edition & the TI-84 Plus Silver Edition, and FF for the TI-84+CSE.</nowiki><br>
-<nowiki>**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.</nowiki>
+<nowiki>**1B for the TI-83 Plus, 3B for the TI-84 Plus, 7B for the TI-83 Plus Silver Edition & the TI-84 Plus Silver Edition, and 05 for the TI-84+CSE.</nowiki>

@@ Line 19: / Line 19: @@
 Once the OS has mapped the appropriate page into 4000-7FFF, it uses the number as a pointer to a vector on this page. On pages 1B and 1F there are lists of vectors for the actual ROM routines. Each vector is 3 bytes - the first two bytes are a memory address and the third byte is the page that the routine is on.
 <nowiki>*1F for the TI-83 Plus, 3F for the TI-84 Plus and 7F for the TI-83 Plus Silver Edition & the TI-84 Plus Silver Edition.</nowiki><br>
 <nowiki>**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.</nowiki>
 == See Also ==
 * [[83Plus:OS:ROMPage1B|ROM Page 1B]]

← Older revision		Revision as of 20:01, 9 April 2006
Line 24:		Line 24:
	<nowiki>*1F for the TI-83 Plus, 3F for the TI-84 Plus and 7F for the TI-83 Plus Silver Edition & the TI-84 Plus Silver Edition.</nowiki><br>		<nowiki>*1F for the TI-83 Plus, 3F for the TI-84 Plus and 7F for the TI-83 Plus Silver Edition & the TI-84 Plus Silver Edition.</nowiki><br>
	<nowiki>**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.</nowiki>		<nowiki>**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.</nowiki>
		+
		+	== See Also ==
		+	* [[83Plus:OS:ROMPage1B\|ROM Page 1B]]

← Older revision		Revision as of 09:05, 10 September 2005
Line 1:		Line 1:
		+	[[Category:83Plus:OS_Information\|How BCALLs work]]
	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.		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.

@@ Line 7: / Line 7: @@
 *It resets bit 15
 *It adds 0x4000 to the number
-*It maps page 1F into memory space 4000-7FFF
+*It maps page 1F/3F/7F* into memory space 4000-7FFF
 Otherwise, if bit 15 is reset and bit 14 is set, this is what the OS does:
@@ Line 13: / Line 13: @@
 *It resets bit 14
 *It adds 0x4000 to the number
-*It maps page 1B into memory space 4000-7FFF
+*It maps page 1B/3B/7B** into memory space 4000-7FFF
 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.
 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.

@@ Line 2: / Line 2: @@
 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.
-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.
+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, followed by a 16-bit number which is used to identify the routine it is calling.
 If the first bit (bit 15) of the number is set, this is what the OS does:
@@ Line 18: / Line 18: @@
 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.
-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.
+Once the OS has mapped the appropriate page into 4000-7FFF, it uses the number as a pointer to a vector on this page. On pages 1B and 1F there are lists of vectors for the actual ROM routines. Each vector is 3 bytes - the first two bytes are a memory address and the third byte is the page that the routine is on.