Rst Routines; System Ram Areas; System Flags - Texas Instruments TI-83 Plus Manual

12

RST Routines

The Z80 restart instruction, RST, can be used in place of B_CALL for some entry points.
Using the RST instruction only takes one byte of ROM space as opposed to three bytes
for a B_CALL. There are five routines set to use this method of access. These were
chosen because of high-frequency use in the operating system.
RST rMov9ToOP1
RST rFindSym
RST rPushRealO1
RST rOP1ToOP2
RST rFPAdd
Details on these routines can be found in this chapter or in the System Routine
Documentation.

System RAM Areas

The details about system RAM follow.

System Flags

This area of RAM is used for bit flags. The TI-83 Plus accesses these flags through the
Z80's IY register. The IY register is set to the start of this flag area and does not
change, resulting in easy bit manipulation.
Example:
trigFlags is the byte offset from the start of the flag area.
Some system flags that an application might use are listed in Table 2.1, along with
information needed to support basic ASM programming on the TI-83 Plus.
The values for these symbols are located in the include file, TI83plus.inc.
TI-83 Plus Developer Guide
used instead of
used instead of
used instead of
used instead of
used instead of
SET trigDeg,(IY+trigFlags)
Chapter 2: TI-83 Plus Specific Information
B_CALL Mov9ToOP1
B_CALL FindSym
B_CALL PushRealO1
B_CALL OP1ToOP2
B_CALL FPAdd
; set to degree angle mode
Third Release May 28, 2002