35 lines
974 B
NASM
35 lines
974 B
NASM
;;
|
|
;; function: div10_unsigned
|
|
;;
|
|
|
|
;; argument: y
|
|
;; return: a ← y / 10
|
|
;; maximum y is somewhere between 2 ^ 21 and 2 ^ 22
|
|
div10_unsigned:
|
|
;; 1 / 10 * (2 ^ 24) ~= 1677722 = 0x19999a
|
|
mvi 1677722,rx
|
|
mov mul,p clr a
|
|
ad2 mov alu,a
|
|
|
|
;; ALH: [nmlkjihgfedcba9876543210________]
|
|
;; ALL: [76543210________________________]
|
|
|
|
clr a mov alh,pl ; alh is (a >> 16)
|
|
add mov alu,a
|
|
|
|
;; ALL: [nmlkjihgfedcba9876543210________]
|
|
|
|
;; rotate left 24 requires fewer cycles than shift right 8
|
|
rl8 mov alu,a
|
|
rl8 mov alu,a
|
|
rl8 mov alu,a
|
|
|
|
;; ALL: [________nmlkjihgfedcba9876543210]
|
|
|
|
;; mask 24 bit result
|
|
mvi 0xffffff,pl
|
|
|
|
;; return to caller; reset caller's ct2
|
|
btm
|
|
and mov alu,a mov 0,ct2
|