Help in paging 16F877 - Electronic Circuits Projects Diagrams Free

TronicBrain · 29th April 2007, 10:45 PM

Hi
This is the first time I reach about 550 instruction set in 16F877
But it started causing troubles

My code is about several subroutines called from the main program
At the beginning of the project I was adding the code piece after piece
And make a test after adding every sub routine
(all the subroutines are working well individually)

But when added the last piece of code it dose not work
When moving it after the main program
It works but leaving the last piece of code not working!

I thing it's a matter of paging the program memory

I do not know how to deal with PCLATH register
and my whole program will not exceed 700 instruction set

any help?

Pommie · 30th April 2007, 01:10 AM

If your code is not going to exceed 700 instructions then it will fit in one bank. The bank size if 2048 (0x800) instructions. It is more likely that a table is moving and crossing a page boundary. Look for any access to PCL and check that the table that follows is all in one page - IE has the same high byte in the address.

If your code is going over 2k then you can call subroutines in the far bank by doing the following,

Code:

		movlw	high(FarSub)
		movwf	PCLATH
		call	FarSub
		clrf	PCLATH

Or,

Code:

		bsf	PCLATH,3
		call	FarSub
		bcf	PCLATH,3

Note that once you are in bank 2 then all calls and gotos will stay in bank 2 until you "return" to bank 1.

Mike.

**Nigel Goodwin** · 30th April 2007, 09:41 AM

There's also a Microchip macro 'fcall', which generates the required code for you:

Code:

; Macros
fcall    macro subroutine_name
    local here
    lcall subroutine_name
    pagesel here
here:
    endm

To use it just add it to the header of your program and use fcall instead of call for your subroutines.

Sceadwian · 1st May 2007, 01:47 AM

This is one of the reasons I decided not to use PIC's, pageing is a pain.

blueroomelectronics · 1st May 2007, 02:12 AM

Quote:

Originally Posted by Sceadwian

This is one of the reasons I decided not to use PIC's, pageing is a pain.

So use the 18F series, very little paging.

TronicBrain · 1st May 2007, 10:26 AM

I put all the subroutines which contain tables in the beginning of the program memory
and the problem is solved

thanks guys

gramo · 2nd May 2007, 03:16 PM

Quote:

Originally Posted by blueroomelectronics

So use the 18F series, very little paging.

18F's are easier to use at the end of the day. 16F's are so old school now.

If anything, with the release of 24F and dsPIC's, the 18F's should be the new mid-range devices

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29th April 2007, 10:45 PM	(permalink)
TronicBrain	Help in paging 16F877 Hi This is the first time I reach about 550 instruction set in 16F877 But it started causing troubles My code is about several subroutines called from the main program At the beginning of the project I was adding the code piece after piece And make a test after adding every sub routine (all the subroutines are working well individually) But when added the last piece of code it dose not work When moving it after the main program It works but leaving the last piece of code not working! I thing it's a matter of paging the program memory I do not know how to deal with PCLATH register and my whole program will not exceed 700 instruction set any help? __________________ I’m from Syrian Arab Republic where lots of guys are trying to do better in electronics.

30th April 2007, 01:10 AM	(permalink)
Pommie	If your code is not going to exceed 700 instructions then it will fit in one bank. The bank size if 2048 (0x800) instructions. It is more likely that a table is moving and crossing a page boundary. Look for any access to PCL and check that the table that follows is all in one page - IE has the same high byte in the address. If your code is going over 2k then you can call subroutines in the far bank by doing the following, Code: movlw high(FarSub) movwf PCLATH call FarSub clrf PCLATH Or, Code: bsf PCLATH,3 call FarSub bcf PCLATH,3 Note that once you are in bank 2 then all calls and gotos will stay in bank 2 until you "return" to bank 1. Mike.

30th April 2007, 09:41 AM	(permalink)
Nigel Goodwin	There's also a Microchip macro 'fcall', which generates the required code for you: Code: ; Macros fcall macro subroutine_name local here lcall subroutine_name pagesel here here: endm To use it just add it to the header of your program and use fcall instead of call for your subroutines. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

1st May 2007, 01:47 AM	(permalink)
Sceadwian	This is one of the reasons I decided not to use PIC's, pageing is a pain. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

1st May 2007, 10:26 AM	(permalink)
TronicBrain	I put all the subroutines which contain tables in the beginning of the program memory and the problem is solved thanks guys __________________ I’m from Syrian Arab Republic where lots of guys are trying to do better in electronics.