The Weeder Frequency Counter
Expanded by Brad Hernlem
3 byte count, 8 digits, 1Hz resolution below 16MHz
;******************************************************************************
; FREQUENCY COUNTER
; Model : WTCNT
; Author : Terry J. Weeder
; Date : November 18, 1993
; Version: 1.0
;
; WWW.WEEDTECH.COM
;
; Ported to 16f84 by
; Peter Cousens
; October 1998
;
; Further revised,
; expanded and modified by
; Brad Hernlem
; October 2000
;******************************************************************************
; This version is changed to use the full capability to count to 3 byte
; quantities (16,777,215) and disables the overflow at 10,000,000 originally
; in Cousens' code. Also, 8 digits are used instead of seven and the gate
; times are set to 1 second to allow 1 Hz resolution on all ranges.
; When the frequency exceeds 16,777,215 Hz the gate period is
; reduced to 0.1 second to keep the count within 3 bytes. When frequency is
; again less than 16,777,216 Hz the gate period reverts to 1 second.
; Please also note that the register addresses are now designated in a
; CBLOCK. This means that any changes to the CBLOCK MUST NOT affect the
; fixed addresses of the digs to digs+7 registers which SHOULD begin at
; 0C and increase from there. If these are changed, the FSR indirect
; addressing will be munged.
;
; Other changes:
;
; 1) the LCD control pins are reassigned to be compatible with Halicky's code
; 2) the display reads "0" when no pulses are inputted. Cousens' code included
; an rtcc toggle of unknown use which gave an output of "1" without input.
; 3) display shows message "Counting" during initial 1 second count delay.
;
; [Brad Hernlem]
;
; FCounter.ASM
;***************************************************************************
list P=PIC16F84A
INCLUDE <P16f84a.inc>
__CONFIG _CP_OFF & _WDT_OFF & _XT_OSC & _PWRTE_ON
rtcc equ 1h
c equ 0h
z equ 2h
o equ 7h
rs equ 0h ;This bits were changed for compatibility
rw equ 1h ;with other counter
e equ 2h ;routines (e.g. Halicky)
;Cousens had the following hard designated. CBLOCK makes them float
;but BEWARE that digs is addressed by FSR and MUST NOT be changed from
;the first position of this block
CBLOCK h'0C'
digs:8 ;the display digits registers digs to digs+7
count1
count2
addcnt
gate
cnt1
cnt2
cnt3
calc1
calc2
calc3
sum1
sum2
sum3
rtcc2
temp1
temp2
temp3
cnt4
ENDC
;
org 0
goto start
;
int_del movlw 0x05 ;delay 5.000 ms (4 MHz clock)
movwf count1
d1 movlw 0xA5
movwf count2
d2 decfsz count2,f
goto d2
decfsz count1,f
goto d1
retlw 0x00
;
lcd_out movwf PORTB ;load data into PORTB
movlw b'00000000' ;define PORTB as output
tris PORTB
bsf PORTA,rs ;rs = data
bcf PORTA,rw ;r/w = write
bsf PORTA,e ;toggle enable
bcf PORTA,e
movlw b'11111111' ;define PORTB as input
tris PORTB
bcf PORTA,rs ;rs = instruction
bsf PORTA,rw ;r/w = read
bsf PORTA,e ;enable high
movf PORTB,w ;get address counter
movwf addcnt
bsf addcnt,7
bcf PORTA,e ;enable low
out1 bsf PORTA,e ;enable high
btfss PORTB,7 ;test busy flag
goto out2
bcf PORTA,e ;enable low
goto out1
out2 bcf PORTA,e ;enable low
goto shift
;
inst movwf PORTB ;load instruction into PORTB
movlw b'00000000' ;define PORTB as output
tris PORTB
bcf PORTA,rs ;rs = instruction
bcf PORTA,rw ;r/w = write
bsf PORTA,e ;toggle enable
bcf PORTA,e
movlw b'11111111' ;define PORTB as input
tris PORTB
bsf PORTA,rw ;r/w = read
inst1 bsf PORTA,e ;enable high
btfss PORTB,7 ;test busy flag
goto inst2
bcf PORTA,e ;enable low
goto inst1
inst2 bcf PORTA,e ;enable low
retlw 0x00
;
shift btfss addcnt,0 ;shift to opposite side of display?
retlw 0x00
btfss addcnt,1
retlw 0x00
btfss addcnt,2
retlw 0x00
btfss addcnt,3
retlw 0x00
movlw 0x39
addwf addcnt,f
bsf addcnt,7
movf addcnt,w
goto inst
;
sub bcf STATUS,o ;clear overflow bit
movf calc1,w ;subtract calc1 from cnt1
subwf cnt1,f
btfsc STATUS,c
goto sb1
movlw 0x01 ;borrow from cnt2 if overflow
subwf cnt2,f
btfsc STATUS,c
goto sb1
subwf cnt3,f ;borrow from cnt3 if cnt2 overflow
btfss STATUS,c
bsf STATUS,o ;set overflow bit if result is negative
sb1 movf calc2,w ;subtract calc2 from cnt2
subwf cnt2,f
btfsc STATUS,c
goto sb2
movlw 0x01 ;borrow from cnt3 if cnt2 overflow
subwf cnt3,f
btfss STATUS,c
bsf STATUS,o ;set overflow bit if result is negative
sb2 movf calc3,w ;subtract calc3 from cnt3
subwf cnt3,f
btfss STATUS,c
bsf STATUS,o ;set overflow bit if result is negative
retlw 0x00
;
add movf calc1,w ;add calc1 to cnt1
addwf cnt1,f
btfss STATUS,c
goto ad1
incfsz cnt2,f ;add to cnt2 if cnt1 overflow
goto ad1
incf cnt3,f ;add to cnt3 if cnt2 overflow
ad1 movf calc2,w ;add calc2 to cnt2
addwf cnt2,f
btfsc STATUS,c
incf cnt3,f ;add to cnt3 if cnt2 overflow
movf calc3,w ;add calc3 to cnt3
addwf cnt3,f
retlw 0x00
;
; The following has been modified to extract 8 digits
; and get 1 Hz accuracy up to the full 3 byte limit of 16,777,215
;
cnvt movlw 0x08 ;8 digits in display
movwf count1
movlw 0x0C ;set fsr for MSB in display
movwf FSR
movlw 0x2F ;one less that ASCII "0"
cnvt0 movwf INDF
incf FSR,f
decfsz count1,f
goto cnvt0
movlw 0x98 ;load "10,000,000" in calc1-3
movwf calc3
movlw 0x96
movwf calc2
movlw 0x80
movwf calc1
cnvt1 call sub ;subtract 10 million from count
incf digs,f ;increment 10,000,000s register
btfss STATUS,o ;check if overflow
goto cnvt1
call add ;add back last number
movlw 0x0F ;load "1,000,000" in calc1-3
movwf calc3
movlw 0x42
movwf calc2
movlw 0x40
movwf calc1
cnvt2 call sub ;subtract number from count
incf digs+1,f ;increment 1,000,000's register
btfss STATUS,o ;check if overflow
goto cnvt2
call add ;add back last number
movlw 0x01 ;load "100,000" in calc1-3
movwf calc3
movlw 0x86
movwf calc2
movlw 0xA0
movwf calc1
cnvt3 call sub ;subtract number from count
incf digs+2,f ;increment 100,000's register
btfss STATUS,o ;check if overflow
goto cnvt3
call add ;add back last number
clrf calc3 ;load "10,000" in calc1-3
movlw 0x27
movwf calc2
movlw 0x10
movwf calc1
cnvt4 call sub ;subtract number from count
incf digs+3,f ;increment 10,000's register
btfss STATUS,o ;check if overflow
goto cnvt4
call add ;add back last number
movlw 0x03 ;load "1,000" in calc1-3
movwf calc2
movlw 0xE8
movwf calc1
cnvt5 call sub ;subtract number from count
incf digs+4,f ;increment 1,000's register
btfss STATUS,o ;check if overflow
goto cnvt5
call add ;add back last number
clrf calc2 ;load "100" in calc1-3
movlw 0x64
movwf calc1
cnvt6 call sub ;subtract number from count
incf digs+5,f ;increment 100's register
btfss STATUS,o ;check if overflow
goto cnvt6
call add ;add back number
movlw 0x0A ;load "10" in calc1-3
movwf calc1
cnvt7 call sub ;subtract number from count
incf digs+6,f ;increment 10's register
btfss STATUS,o ;check if overflow
goto cnvt7
call add ;add back last number
movf cnt1,w ;put remainder in 1's register
addwf digs+7,f
incf digs+7,f
retlw 0x00
;
; Count period is 25*count2*count1 clocks
; for 4MHz crystal with count2=200, count1=20 gives 0.1 s gate period
; count1=200 gives 1 s gate period
;
count movlw b'00110111' ;rtcc = ext, 1/256
option
movlw b'00010000' ;define PORTA as output
tris PORTA
bcf PORTA,3
bcf PORTA,rs
clrf cnt3
clrf cnt4
clrf temp3
clrf rtcc
clrf rtcc2
; bsf PORTA,rs ;toggle rtcc pin
; bcf PORTA,rs ;[these two lines were in Cousens' code. purpose unkown]
movf gate,w ;get gate time
movwf count1
st1 bsf PORTA,3 ;start count
fr4 movlw 0xC8 ;1 count2 set to 200
movwf count2 ;2
goto fr6 ;4
fr5 nop ;24
nop ;25
nop ;01
nop ;02
nop ;03
nop ;04
fr6 movf rtcc,w ;5 test for rtcc rollover (12)
subwf rtcc2,f ;6
btfss STATUS,z ;7
goto fr7 ;9
nop ;9
goto fr8 ;11
fr7 btfsc STATUS,c ;10
incf cnt3,f ;11
fr8 movwf rtcc2 ;12
movf cnt3,w ;13 test for cnt3 rollover
subwf temp3,f ;14
btfss STATUS,z ;15
goto br1 ;17
nop ;17
goto br2 ;19
br1 btfsc STATUS,c ;18
incf cnt4,f ;19 increment cnt4 if cnt3 rollover
br2 movwf temp3 ;20
decfsz count2,f ;21
goto fr5 ;23
decfsz count1,f ;23+25(count2-1)
goto fr4 ;25
bcf PORTA,3 ;25*count2*count1 stop count
st2 movf rtcc,w ;get rtcc count
movwf cnt2
subwf rtcc2,f ;test for rtcc rollover
btfss STATUS,c
goto fr9
btfss STATUS,z
incf cnt3,f
fr9 clrf cnt1 ;set to get prescaler count
fr10 decf cnt1,f
bsf PORTA,rs ;toggle rtcc pin
bcf PORTA,rs
movf rtcc,w ;test if rtcc has changed
xorwf cnt2,w
btfsc STATUS,z
goto fr10
retlw 0x00
;
;******************************************************************************
; START
;******************************************************************************
;
start clrf PORTA ;instruction, write, enable low
movlw b'00010000'
tris PORTA
clrf PORTB
movlw b'00000000'
tris PORTB
call int_del
call int_del
call int_del
movlw 0x38 ;initialize display
movwf PORTB
bsf PORTA,e ;toggle enable
call int_del
bcf PORTA,e
bsf PORTA,e ;toggle enable
call int_del
bcf PORTA,e
bsf PORTA,e ;toggle enable
call int_del
bcf PORTA,e
movlw 0x38 ;function
call inst
movlw b'00001100' ;display on, cursor off
call inst
movlw b'00000001' ;clear display
call inst
movlw b'00000110' ;entry mode
call inst
; Intro message during initial count
movlw 0x20 ;space
call lcd_out
movlw 0x20 ;space
call lcd_out
movlw 0x20 ;space
call lcd_out
movlw 0x20 ;space
call lcd_out
movlw 0x43 ;C
call lcd_out
movlw 0x6F ;0
call lcd_out
movlw 0x75 ;u
call lcd_out
movlw 0x6E ;n
call lcd_out
movlw 0x74 ;t
call lcd_out
movlw 0x69 ;i
call lcd_out
movlw 0x6E ;n
call lcd_out
movlw 0x67 ;g
call lcd_out
;
mhz movlw 0xC8 ;1 sec gate
movwf gate
call count
clrw ;check whether cnt4 is zero
xorwf cnt4,w
btfss STATUS,z
goto shortg ;not zero - use shorter gate period
call cnvt ;convert binary to BCD
movlw 0x30 ;test if "0"
xorwf digs,w
btfss STATUS,z
goto mhz1
movlw 0x30 ;test if "0"
xorwf digs+1,w
btfsc STATUS,z
goto khz1
mhz1 movlw 0x81 ;set display address
call inst
movlw 0x02 ;output first 2 characters
movwf count1
movlw 0x0C ;MSD of freq, i.e. digs
movwf FSR
mhz2 movlw 0x30 ;test if "0"
xorwf INDF,w
btfss STATUS,z
goto mhz3
movlw 0x20 ;change preceeding "0's" to "space"
call lcd_out
incf FSR,f
decfsz count1,f
goto mhz2
goto mhz4
mhz3 movf INDF,w
call lcd_out
incf FSR,f
decfsz count1,f
goto mhz3
mhz4 movlw 0x2E ;"."
call lcd_out
movlw 0x06 ;output last 6 characters
movwf count1
mhz5 movf INDF,w
call lcd_out
incf FSR,f
decfsz count1,f
goto mhz5
movlw 0x20 ;"space"
call lcd_out
movlw 0x4D ;"M"
call lcd_out
movlw 0x48 ;"H"
call lcd_out
movlw 0x7A ;"z"
call lcd_out
movlw 0x20 ;"space"
call lcd_out
movlw 0x20 ;"space"
call lcd_out
goto mhz
;
khz movlw 0xC8 ;1 sec gate
movwf gate
call count
call cnvt ;convert binary to BCD
movlw 0x30 ;test if 0
xorwf digs,w
btfss STATUS,z
goto mhz1
movlw 0x32 ;test if < 2
subwf digs+1,w
btfsc STATUS,c
goto mhz1
movlw 0x30 ;test if "0"
xorwf digs+1,w
btfss STATUS,z
goto khz1
movlw 0x30 ;test if "0"
xorwf digs+2,w
btfss STATUS,z
goto khz1
movlw 0x30 ;test if "0"
xorwf digs+3,w
btfsc STATUS,z
goto hz0
khz1 movlw 0x81 ;set display address
call inst
movlw 0x05 ;output first 5 characters
movwf count1
movlw 0x0C ;MSD of freq, digs register
movwf FSR
khz2 movlw 0x30 ;test if "0"
xorwf INDF,w
btfss STATUS,z
goto khz3
movlw 0x20 ;change preceeding "0's" to "space"
call lcd_out
incf FSR,f
decfsz count1,f
goto khz2
goto khz4
khz3 movf INDF,w
call lcd_out
incf FSR,f
decfsz count1,f
goto khz3
khz4 movlw 0x2E ;"."
call lcd_out
movf INDF,w ;output last 3 characters
call lcd_out
incf FSR,f
movf INDF,w
call lcd_out
incf FSR,f
movf INDF,w
call lcd_out
movlw 0x20 ;"space"
call lcd_out
movlw 0x4B ;"K"
call lcd_out
movlw 0x48 ;"H"
call lcd_out
movlw 0x7A ;"z"
call lcd_out
movlw 0x20 ;"space"
call lcd_out
movlw 0x20 ;"space"
call lcd_out
goto khz
;
hz movlw 0xC8 ;1 sec gate
movwf gate
call count
call cnvt ;convert binary to BCD
movlw 0x30 ;test if "0"
xorwf digs,w
btfss STATUS,z
goto mhz1
movlw 0x32 ;test if < 2
subwf digs+1,w
btfsc STATUS,c
goto mhz1
movlw 0x30 ;test if "0"
xorwf digs+1,w
btfss STATUS,z
goto khz1
movlw 0x30 ;test if "0"
xorwf digs+2,w
btfss STATUS,z
goto khz1
movlw 0x30 ;test if "0"
xorwf digs+3,w
btfss STATUS,z
goto khz1
hz0 movlw 0x81 ;set display address
call inst
movlw 0x07 ;output first 7 characters
movwf count1
movlw 0x0C ;MSD of freq, digs register
movwf FSR
hz1 movlw 0x30 ;test if "0"
xorwf INDF,w
btfss STATUS,z
goto hz2
movlw 0x20 ;change preceeding "0's" to "space"
call lcd_out
incf FSR,f
decfsz count1,f
goto hz1
goto hz3
hz2 movf INDF,w
call lcd_out
incf FSR,f
decfsz count1,f
goto hz2
hz3 movf INDF,w
call lcd_out
movlw 0x20 ;"space"
call lcd_out
movlw 0x48 ;"H"
call lcd_out
movlw 0x7A ;"z"
call lcd_out
movlw 0x20 ;"space"
call lcd_out
movlw 0x20 ;"space"
call lcd_out
movlw 0x20 ;"space"
call lcd_out
movlw 0x20 ;"space"
call lcd_out
goto hz
;
shortg movlw 0x14 ;0.1 sec gate
movwf gate
call count
call tenx ;multiply count by ten
clrw ;check whether cnt4 is zero
xorwf cnt4,w
btfsc STATUS,z
goto mhz ;was zero - use longer gate period
call cnvt ;convert binary to BCD
movlw 0x30 ;test if "0"
xorwf digs,w
btfss STATUS,z
goto shg1
movlw 0x30 ;test if "0"
xorwf digs+1,w
btfsc STATUS,z
goto mhz
shg1 movlw 0x81 ;set display address
call inst
movlw 0x03 ;output first 3 characters
movwf count1
movlw 0x0C ;MSD of freq, i.e. digs
movwf FSR
shg2 movlw 0x30 ;test if "0"
xorwf INDF,w
btfss STATUS,z
goto shg3
movlw 0x20 ;change preceeding "0's" to "space"
call lcd_out
incf FSR,f
decfsz count1,f
goto shg2
goto shg4
shg3 movf INDF,w
call lcd_out
incf FSR,f
decfsz count1,f
goto shg3
shg4 movlw 0x2E ;"."
call lcd_out
movlw 0x05 ;output last 5 characters
movwf count1
shg5 movf INDF,w
call lcd_out
incf FSR,f
decfsz count1,f
goto shg5
movlw 0x20 ;"space"
call lcd_out
movlw 0x4D ;"M"
call lcd_out
movlw 0x48 ;"H"
call lcd_out
movlw 0x7A ;"z"
call lcd_out
movlw 0x20 ;"space"
call lcd_out
movlw 0x20 ;"space"
call lcd_out
goto shortg
;
; This subroutine multiplies the count in cnt1-3 by 10 (called from the 0.1 sec
; gate routine) and puts any overflow into cnt4. This is to check whether the frequency
; has gone back under 16,777,216 and whether the gate period should be increased to 1 sec.
;
tenx clrf cnt4 ;clear the overflow register and
movf cnt1,w ;fill calc1-3 with current cnt1-3 values
movwf calc1 ;it is assumed that cnt4 cannot be non-zero
movf cnt2,w ;when the gate period is only 0.1 sec
movwf calc2 ;
movf cnt3,w ;
movwf calc3 ;
bcf STATUS,c
rlf calc1,f ;multiply by 2 and carry through
rlf calc2,f
rlf calc3,f
btfsc STATUS,c
incf cnt4,f
movf calc1,w ;temporarily store the times 2 value
movwf temp1
movf calc2,w
movwf temp2
movf calc3,w
movwf temp3
bcf STATUS,c
rlf calc1,f ;multiply by 2 twice and check for carry each time
rlf calc2,f
rlf calc3,f
btfsc STATUS,c
incf cnt4,f
bcf STATUS,c
rlf calc1,f
rlf calc2,f
rlf calc3,f
btfsc STATUS,c
incf cnt4,f
movf temp1,w ;now add the x2 and x8 values for x10 total
addwf calc1,f
btfsc STATUS,c
incf calc2, f
btfsc STATUS,z
incf calc3,f
btfsc STATUS,z
incf cnt4,f
movf temp2,w
addwf calc2,f
btfsc STATUS,c
incf calc3,f
btfsc STATUS,z
incf cnt4,f
movf temp3,w
addwf calc3,f
btfsc STATUS,c
incf cnt4,f
return
;
end
| file: /Techref/piclist/weedfreq/8digit.asm, 22KB, , updated: 2006/4/7 14:43, local time: 2024/4/19 08:23,
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