2.3 Relaxatie-oscillator

fr_6: jb sensor,fr_6 ;loop during sensor is hi
mov R3,#num_per ;temporarily counter for number of captures
mov OP_0,#000 ;not used
mov OP_1,#000 ;possible carry from TH1 (updated in TIMER1)
setb EX0 ;enable EX0 (but not yet EA)
setb ET1 ;enable interrupt from timer1 overflow
fr_strt: jnb sensor,fr_strt ;loop during sensor is lo
fr_h2l: jb sensor,fr_h2l ;loop during sensor is hi
setb TR1 ;timer1 runs: start with measuring
clr IE0 ;no hardware to reset, so software does this task now
setb EA ;enable interrupts (vectored to EXT0)
fr_loop: cjne R3,#000,fr_loop ;wait for num_rep captured timingdata
;R3 is decreased through int. routine EXTI0
clr EA ;finished measuring, disable all interrupts
clr TR1 ;stop timer1
clr EX0 ;disable _INT0
clr ET1 ;disable interrupt from timer1
mov OP_2,TH1 ;timer1 MSB result in OP_2
mov OP_3,TL1 ;timer1 LSB result in OP_3
mov R2,#000 ;MSB of divider
mov R3,#num_per ;LSB of divider
acall Div_16 ;calc.: OP_(0..3) \ num_per =
mov prd_h,OP_2 ;store result counting in prd
mov prd_l,OP_3 ;store result counting in prd
mov C,wvmem ;put port sensctrl through carry in original state
mov sensctrl,C
setb EA ;enable interrupts
ret ;ready with measuring & calculating
;*******************************************************************************
;* wavectrl -> wvmem,vldsns *
;* interrupt from timer0 occurred, so there’s some work to do. Precalculated *
;* values for TH0 & TL0 determine how long the hi-state (in hi_TH0 & hi_TL0) *
;* for vldsns=0 and (hivdTH0 & hivdTL0) for vldsns=1 lasts, followed by how *
;* long lo-state (in lo_TH0 & lo_TL0) on output port sensctrl will last. *
;*