Dear Russell,

My apologies if the explanation so far seem to make no sense at all. This is the 1st time that I'm using a PCA, thus your assistance is much appreciated.

1. The chip simulated is P89C51RD2HBA.

2. Application to generate a linear frequency ramp from 1Khz ~ 40 Khz at increments of 1 Khz.

3. All values have been confirmed to produce the correct frequency & number of pulses using a scope. However at higher frequencies, my suspicions is that something is causing a delay when the PCA is switching frquencies. This is only seen after 16Khz, but not at lower frquencies.

4. My code :

Non_Value holds the number of pulses which is needed.
Value1 is incremented everytime a pulses is generated.


.Main_Program:

Lcall F_Counter_up


PCA_INIT: ;Initializa PCA Timer
MOV CMOD,#02H ; Input to PCA Timer = 1/4 * Fosc
MOV CH,#00
MOV CL,#00
MOV CCAPM0,#04DH ; HSO with Interrupt Enabled
MOV CCAP0L,#.LOW(1000) ; Not sure what this does !!!!!
MOV CCAP0H,#.HIGH(1000); Not sure what this does !!!!!
CLR P1.3
SETB EC ; Enable PCA Interrupt
SETB EA
SETB CR
MOV VALUE1,#0

WAIT: ; The following routine controls number of pulses needed
MOV A,VALUE1
cjne a,NON_PULSES,done1
MOV CCAPM0,#00H ; Disable HSO mode
RET

done1: SJMP wait ; Loop number of pulses equals

PCA_INTERRUPT:
CLR CCF0
JNB P1.3,DONE
done2:
PUSH ACC
PUSH PSW
CLR EA
MOV A,FREQ1
ADD A,CCAP0L
MOV CCAP0L,A
MOV A,FREQ2

ADDC A,CCAP0H
MOV CCAP0H,A
SETB EA

POP PSW
POP ACC

RETI

DONE:
inc value1
sjmp done2


F_COUNTER_UP:
MOV FREQ1,#.LOW(3125) ; 1kHZ using 25Mhz Crystal
MOV FREQ2,#.HIGH(3125)
MOV NON_PULSES,#100 ; Number of pulses needed
LCALL PCA_INIT

MOV FREQ1,#.LOW(1563) ; 2Khz using 25Mhz Crystal
MOV FREQ2,#.HIGH(1563)
MOV NON_PULSES,#100 ; Number of pulses needed
LCALL PCA_INIT

; Balance of code is here ( truncated for explanation )

MOV FREQ1,#.LOW(78) ; 40 Khz using 25Mhz Crystal
MOV FREQ2,#.HIGH(78)
MOV NON_PULSES,#100 ; Number of pulses needed
LCALL PCA_INIT

RET


P.S : I've got Cool Edit, however how would one use it to see the pulses