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Information for Assembly Programmers |
TI's OS for TI-68k calculators, AMS, has a rich set of built-in functions, but unfortunately many
of them are not yet documented by TI. However, some entry points are documented. As many functions
which I defined in this library are just OS calls, the documentation of these functions is also
the documentation of OS calls.
This means that this document documents more than 600 OS calls, so it may be very valuable
for assembly programers. When the function is nothing more than simple OS call, I give to it
either the name used in TI's list of OS entry points, or a name invented by someone. So you can
easily determine which functions are simple OS calls.
Of course, function parameters are listed using the C language calling convention, because this is a library for C programing. If you are an assembly programmer, you need to know the following:
DrawClipEllipse (100, 50, 30, 20, &(SCR_RECT){{0, 0, 159, 99)}, A_NORMAL);in the ASM program, you should do the following code (kernel calling convention will be assumed, due to simplicity):
move.w #1,-(sp) pea clip(pc) move.w #20,-(sp) ; Using move.l #$1E0014,-(sp) you can pack move.w #30,-(sp) ; these two ASM instructions into one move.w #50,-(sp) move.w #20,-(sp) jsr tios::DrawClipEllipse lea (sp,14),sp ; The same as add.l #14,sp but shorter ... clip: dc.b 0,0,159,99 ; Components of SCR_RECT structure are bytes
float
type and bcdmul & bcdlong to work with bcd structures; at the fundamental ASM level they are exactly the same routines). Then, this calculation may be performed using the following ASM program:
lea after(pc),a6 ; Prepare a6 for storing results clr.l -(sp) ; Push 342.1178 move.l #$34211780,-(sp) move.w #$4002,-(sp) jsr tios::log ; The result is now in "temp" move.l (a6,-4),-(sp) ; Push the result move.l (a6,-8),-(sp) move.w (a6,-10),-(sp) clr.l -(sp) ; Push 2.34 clr.w -(sp) move.l #$40002340,-(sp) jsr tios::bcdmul ; The result is again in "temp" move.l (a6,-4),-(sp) ; Push the result again move.l (a6,-8),-(sp) move.w (a6,-10),-(sp) jsr tios::bcdlong ; The final result is now in d0 lea (sp,40),sp ; Clean up the stack ... temp: ds.b 10 ; Ten-byte buffer after: ...This program may be much more optimized if you know how to use stack frames properly (this technic is so popular in high-level language compilers, but quite unpopular in ASM programs; this example shows that stack frames may be very useful). The optimized version of the same program follows:
link a6,#-10 ; Create 10-bytes long space on the stack clr.l -(sp) ; Push 342.1178 move.l #$34211780,-(sp) move.w #$4002,-(sp) jsr tios::log ; The result is on the stack frame addq.l #6,sp ; Adjust the stack pointer clr.l (sp) ; Push 2.34 clr.w -(sp) move.l #$40002340,-(sp) jsr tios::bcdmul ; The result is again on the stack frame lea (sp,10),sp ; Adjust the stack pointer again jsr tios:bcdlong ; The final result is now in d0 unlk a6 ; Remove the stack frameNote: Some of the information about OS calls given by TI itself on their site is incomplete or even wrong. This document contains more precise information.