Re: A82: ASM code problem


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Re: A82: ASM code problem



At 07:54 PM 7/7/97 -0400, you wrote:
>>   call (FINAL_ADDR)
>
>Well... CALL (FINAL_ADDR) should mean call the address that's stored at
'FINAL_ADDR', but that's not an instruction in Z80 assembly language, so
I'm assuming it's supposed to be CALL_(FINAL_ADDR), which is the
Zshell/Ash/Oshell-82 defines for calling even though the program will be at
another place.

No, I meant call (FINAL_ADDR).  The call opcode does exist (see the Z80
Instruction Set Summary).  The source I sent to this list is only a small
portion of the ROM_CALL routine that I will be using in ASH <-> OShell.  I
sent the source because I wanted to see if there was any errors in my
knowledge of Z80 ASM.  I have narrowed my problem down to just a line or
two of code.  The following code does NOT work:

#include "ti-82.h"
FINAL_ADDR = $8C2B         ; Word

.ORG 0
.DB "Test Ver",0

  call CLEARLCD            ; Clears the LCD
  ld bc,0                  ; 0 -> c, 0 -> b
  ld (CURSOR_ROW),bc       ; Set cursor at position (0,0)
  ld hl,Text               ; Address of Text -> hl
  ld de,(PROGRAM_ADDR)     ; (PROGRAM_ADDR) -> de
  add hl,de                ; hl = hl + de

  ld bc,D_ZT_STR
  ld (FINAL_ADDR),bc
  call (FINAL_ADDR)
GetkeyLoop:
  call GET_KEY             ; Get the keyboard scan code
  cp $37                   ; Check to see if [MODE] was pressed
  ret Z                    ; If so, return to caller
  jr GetkeyLoop            ; Goto GetkeyLoop

Text: .DB "Hello World!!!",0

.END


However, this code works (it gets to be REAL weird after fooling with the
code for a while):

#include "ti-82.h"
FINAL_ADDR = $8C2B         ; Word

.ORG 0
.DB "Test Ver",0

  call CLEARLCD            ; Clears the LCD
  ld bc,0                  ; 0 -> c, 0 -> b
  ld (CURSOR_ROW),bc       ; Set cursor at position (0,0)
  ld hl,Text               ; Address of Text -> hl
  ld de,(PROGRAM_ADDR)     ; (PROGRAM_ADDR) -> de
  add hl,de                ; hl = hl + de

  call D_ZT_STR
GetkeyLoop:
  call GET_KEY             ; Get the keyboard scan code
  cp $37                   ; Check to see if [MODE] was pressed
  ret Z                    ; If so, return to caller
  jr GetkeyLoop            ; Goto GetkeyLoop

Text: .DB "Hello World!!!",0

.END

Both programs should be compiled under OShell-82.  This is a very confusing
problem and I really would like any hint to an answer.

TIA,
Thomas J. Hruska

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