PHP1 V3.8

This version of the display/stabiliser program is for the 
PIC16F84 or PIC16C84 microcontroller using a 4.000MHz 
crystal.

My transceiver has an I.F. frequency of 7.8000MHz. The 
required offsets are 7.79850MHz and 7.80150MHz for 
USB and LSB.  gadget38.asm is the source code for
the current version of the program used in both 
of my home made SSB transceivers.

To change the I.F. offset to a different value, locate 
the label CONVERT in the source code .  The code following 
this label adds/subtracts the I.F. offset to/from the 
VFO frequency.


For example:

ADD_HI	MOVLW	076H			;Add IF 7.80150MHz
		ADDWF	L_BYTE,F
		BTFSC	STATUS,CARRY	;0BE776 HEX = 780150 Dec.
		INCF	M_BYTE,F
		MOVLW	0E7H
		ADDWF	M_BYTE,F
		BTFSC	STATUS,CARRY
		INCF	H_BYTE,F
		MOVLW	00BH
		ADDWF	H_BYTE,F

adds 780150 to the VFO frequency.  780150 decimal = 0BE776 hexadecimal.

Note that the least significant byte is added first and the most 
significant byte is added last.


To save writing additional code for subtracting, the I.F.  is
subtracted by using a well know programmers trick. The subtraction 
is achieved by adding the compliment of the I.F.  Adding -780150 
to a number has the same effect as subtracting +780150.

For example:

	MOVLW	0B6H				;Subtract IF by adding -IF
	ADDWF	L_BYTE,F
	BTFSC	STATUS,CARRY		;-779850 Dec = F419B6 HEX
	INCF	M_BYTE,F
	MOVLW	019H
	ADDWF	M_BYTE,F
	BTFSC	STATUS,CARRY
	INCF	H_BYTE,F
	MOVLW	0F4H
	ADDWF	H_BYTE,F

Subtracts 779850 from the VFO freq. by adding -779850 to the VFO freq.
-779850 = F419B6.   

I use a scientific calculator to do the decimal to hex conversion. When 
my trusty Sharp calculator gets lost under the junk pile, I use kCalc, 
a nice scientific calculator for the KDE desktop.  MS Windows users 
can use the Windows calculator.

This version of the program can subtract the IF from the VFO freq. 
or add the IF to the VFO freq.  I don't have any need to subtract 
the VFO frequency from the IF.  If you need to do this, it should 
be a fairly trivial programming exercise.  I know of at least one 
radio amateur who made this modification.  He has a 40M CW rig 
with a 12MHz I.F.  12 - 4.95 = 7.05


ASSEMBLING THE PROGRAM.
I tried assembling gadget38.asm on several different assemblers.
Gpasm for Linux assembles the file without any errors or warnings.
Mpasm for Dos assembles the file without any errors or warnings.

I had to make a few changes to the source code before I could assemble
it with Picalc for Dos.