HCS12 Assembly Arithmetic -


so learning assembly hcs12 microcontroller.
i need evaluate expression -45+6+(13*2)-(7*4)-65+33. expression needs evaluated left right, following standard order of operations. each operation needs performed on byte values, , can use addition, subtraction, , shifts.

i can evaluate -45+6+(13*2)-(7*4) fine, problems arise when try subtract 65 -41. understand what's going on, don't know how work around it.

edit: should more clear, know happening (the values being truncated). don't know why.

edit2: solved! line ldab #term5 should ldab term5 (same thing next line)

here's code i'm using, reference:

; local defines             term3:  equ 13             term4:  equ 07 ;******************************************************************** myconst:    section ; place constant data here constdata:  dc.b  -45,16 term5:      dc.b  65 term6:      dc.b  33 ;******************************************************************** mycode:     section main: entry:             lds #__seg_end_sstack     ; initialize stack pointer             sei                       ; disable interrupts ; program code goes here main_loop:             nop             ldx   #constdata          ; load -45 , 16 x             ldaa  0,x                 ; load -45 x             ldab  1,x                 ; load 16 x b             aba                       ; add b (a=(-39))             ldab  #term3              ; load 13 b             aslb                      ; shift b left (multiply 2)             aba                       ; add b (a=(-13))             ldab  #term4              ; load 7 b             aslb                      ; shift b left (multiply 2)             asl                       ; shift b left (multiply 2)             sba                       ; subtract b (a=(-41))             ldab  #term5              ; issues start here.             subb  #term6             aba             nop             end ;********************************************************************

(self-answered question.)

per comments:

figured out! turns out when loading constants, don't need # sign. ldab #term5 should ldab term5. – dfryer1193 sep 3 '13 @ 16:32


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