问题
I have written this code for stopwatch in Assembler. If you press button1, it will start counting up. If you press the same button again, it will pause, pressing it once more will resume the stopwatch. Pressing the button number 2 resets the stopwatch.
It is quite some time, since I was programming in PicoBlaze Assembler and this is a few years old code and since I did not program for a few years, I have forgotten a lot. But now I need to slightly alter it and I need your help.
So what I want now is to have the function of counting down. So when I press button1, it will start counting up, pressing it once more will pause it and once more to resume. But pressing the button2 will start counting it down, same with pausing and resuming with the same button and to move the reset from button2 to a new button3.
Can anybody help me with this? Thanks.
VHDL "ROM_blank.vhd", "ProgMem.vhd", "ProgMem"
BUTTON DSIN $00
SWITCH DSIN $01
LED DSOUT $02
SEG0 DSOUT $03
SEG1 DSOUT $04
SEG2 DSOUT $05
SEG3 DSOUT $06
wait0 equ s0
wait1 equ s1
wait2 equ s2
cnt0 equ s3
cnt1 equ s4
cnt2 equ s5
cnt3 equ s6
state equ s7
segsel equ s8
temp equ sf
state_r0 equ 0
state_r1 equ 1
state_s0 equ 2
state_s1 equ 3
decoded_dp equ 254
decoded_0 equ 3
decoded_1 equ 159
decoded_2 equ 37
decoded_3 equ 13
decoded_4 equ 153
decoded_5 equ 73
decoded_6 equ 65
decoded_7 equ 27
decoded_8 equ 1
decoded_9 equ 25
decoded_A equ 5
decoded_B equ 193
decoded_C equ 229
decoded_D equ 133
decoded_E equ 97
decoded_F equ 113
init:
load cnt0, 0
load cnt1, 0
load cnt2, 0
load cnt3, 0
load state, state_s0
start:
; read buttons
in temp, BUTTON
; reset check
and temp, 2
jump z, startstop_check
load cnt0, 0
load cnt1, 0
load cnt2, 0
load cnt3, 0
startstop_check:
in temp, BUTTON
and temp, 1
; state machine
comp state, state_r0
jump z,run0
comp state, state_r1
jump z,run1
comp state, state_s0
jump z, stop0
comp state, state_s1
jump z, stop1
load state, state_s0
stop0:
comp temp, 1
jump nz, fsm_end
load state, state_r0
jump fsm_end
run0:
comp temp, 0
jump nz, fsm_end
load state, state_r1
jump fsm_end
run1:
comp temp, 1
jump nz, fsm_end
load state, state_s1
jump fsm_end
stop1:
comp temp, 0
jump nz, fsm_end
load state, state_s0
fsm_end:
;wait 0.01s
call waitfcn
comp state, state_s0
jump z, decode
comp state, state_s1
jump z, decode
add cnt0, 1
comp cnt0, 10
jump nz, decode
load cnt0, 0
add cnt1, 1
comp cnt1, 10
jump nz, decode
load cnt1, 0
add cnt2, 1
comp cnt2, 10
jump nz, decode
load cnt2, 0
add cnt3, 1
comp cnt3, 10
jump nz, decode
load cnt3, 0
decode:
;decode for output
load temp, cnt0
call decodefcn
out temp, SEG0
load temp, cnt1
call decodefcn
out temp, SEG1
load temp, cnt2
call decodefcn
;add decimal point
and temp, 254
out temp, SEG2
load temp, cnt3
call decodefcn
out temp, SEG3
jump start
decodefcn:
comp temp, 0
jump nz, dec1
load temp, decoded_0
ret
dec1:
comp temp, 1
jump nz, dec2
load temp, decoded_1
ret
dec2:
comp temp, 2
jump nz, dec3
load temp, decoded_2
ret
dec3:
comp temp, 3
jump nz, dec4
load temp, decoded_3
ret
dec4:
comp temp, 4
jump nz, dec5
load temp, decoded_4
ret
dec5:
comp temp, 5
jump nz, dec6
load temp, decoded_5
ret
dec6:
comp temp, 6
jump nz, dec7
load temp, decoded_6
ret
dec7:
comp temp, 7
jump nz, dec8
load temp, decoded_7
ret
dec8:
comp temp, 8
jump nz, dec9
load temp, decoded_8
ret
dec9:
load temp, decoded_9
ret
waitfcn:
load wait2, 25
wt0:
load wait1, 25
wt1 :
load wait0, 200
wt2 :
sub wait0, 1
jump nz, wt2
sub wait1, 1
jump nz, wt1
sub wait2, 1
jump nz, wt0
ret
END
回答1:
Basically it could be done by adding states and copy-editing the code for the second button + moving the second button stuff to the third button. Then there is the editing of upcounting to down counting:
;wait 0.01s
call waitfcn
comp state, state_s0
jump z, decode
comp state, state_s1
jump z, decode
sub cnt0, 1
comp cnt0, 255 ; -1
jump nz, decode
load cnt0, 9
sub cnt1, 1
comp cnt1, 255
...
来源：https://stackoverflow.com/questions/20792185/how-to-reverse-my-stopwatch-code-to-count-down-in-assembler