Quick code question - Electronic Circuits Projects Diagrams Free

imhereithink · 6th September 2007, 09:15 AM

Just checking to see if it is ok to do this, i have stored data into STORE1 and want to check it more than once to see what character it has stored in it. So is this ok the way i am testing the same location for different data?

MOVF STORE1, W
SUBLW D'13'
BTFSC STATUS, Z
RETURN
MOVF STORE1, W
SUBLW D'10'
BTFSC STATUS, Z
RETURN

I was wondering that by calling the same STORE1 again after the sublw, the data held will have changed from the previous sublw? or does it not store the new value after the first sublw?

Hope this makes sense to you guys

Thanks

ericgibbs · 6th September 2007, 09:32 AM

Quote:

Originally Posted by imhereithink

Just checking to see if it is ok to do this, i have stored data into STORE1 and want to check it more than once to see what character it has stored in it. So is this ok the way i am testing the same location for different data?

MOVF STORE1, W
SUBLW D'13'
BTFSC STATUS, Z
RETURN
MOVF STORE1, W
SUBLW D'10'
BTFSC STATUS, Z
RETURN

I was wondering that by calling the same STORE1 again after the sublw, the data held will have changed from the previous sublw? or does it not store the new value after the first sublw?

Hope this makes sense to you guys

Thanks

hi,
As you are not writing W back into the STORE1 after each test, the original STORE1 is not changed.
Also you are reloading W with STORE1 before each new test, its OK.

How many tests are you planning to do on STORE1?

Pommie · 6th September 2007, 09:35 AM

It is fine to do it that way.

There is a better way and that is to use xor. Because xoring the same value twice results in the original value, you can use this to your advantage.

Code:

	MOVF	STORE1, W
	xorlw	D'13' 		; is it 13
	BTFSC	STATUS, Z
	RETURN
	xorlw	D'13'^D'10'	; is it 10
	BTFSC	STATUS, Z
	RETURN
	xorlw	D'10'^'A'	; is it "A"
	BTFSC	STATUS, Z
	goto	CommandA

The ^ symbol tells the assembler to xor the values together.

BTW, when you do any operation with a literal (sublw) the answer always goes in W.

Mike.

imhereithink · 6th September 2007, 09:48 AM

Thanks for clearing that up guys

Eric i am planning on testing STORE1 four times, since i seem to be having sychronisation problems when reading in the received data, so i am wanting to test each bit stored for CR, LF, O, K. That way i should pick up what i am looking for even if it is out of sync.

Thanks again

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6th September 2007, 09:15 AM	(permalink)
imhereithink	Quick code question Just checking to see if it is ok to do this, i have stored data into STORE1 and want to check it more than once to see what character it has stored in it. So is this ok the way i am testing the same location for different data? MOVF STORE1, W SUBLW D'13' BTFSC STATUS, Z RETURN MOVF STORE1, W SUBLW D'10' BTFSC STATUS, Z RETURN I was wondering that by calling the same STORE1 again after the sublw, the data held will have changed from the previous sublw? or does it not store the new value after the first sublw? Hope this makes sense to you guys Thanks Last edited by imhereithink; 6th September 2007 at 09:23 AM.

6th September 2007, 09:35 AM	(permalink)
Pommie	It is fine to do it that way. There is a better way and that is to use xor. Because xoring the same value twice results in the original value, you can use this to your advantage. Code: MOVF STORE1, W xorlw D'13' ; is it 13 BTFSC STATUS, Z RETURN xorlw D'13'^D'10' ; is it 10 BTFSC STATUS, Z RETURN xorlw D'10'^'A' ; is it "A" BTFSC STATUS, Z goto CommandA The ^ symbol tells the assembler to xor the values together. BTW, when you do any operation with a literal (sublw) the answer always goes in W. Mike.

6th September 2007, 09:48 AM	(permalink)
imhereithink	Thanks for clearing that up guys Eric i am planning on testing STORE1 four times, since i seem to be having sychronisation problems when reading in the received data, so i am wanting to test each bit stored for CR, LF, O, K. That way i should pick up what i am looking for even if it is out of sync. Thanks again