What Value to move to PCLATH - Electronic Circuits Projects Diagrams Free

Suraj143 · 17th September 2007, 03:44 AM

Hi I have a terrible problem when writing to PCLATH so please take a look.

I attached the disassembly listing it shows the actual line number in my Data Tables.
You can see the half of Table11 & Table12 exceeding 0FFh mark. Highlighted in red.

I can call Table1 to 10 anywhere in the program memory. Because there in the first 0FFh mark. But when I call Tables 11 & 12 it won’t work very well.

I’m calling Table11 from 12Fh line. Here what I wrote to PCLATH.

Code:

calling Table11 from 12Fh line
	 
        movlw	HIGH Table11
        movwf	PCLATH      
        call	Table11

I think I have missed some PCLATH value any idea.

blueroomelectronics · 17th September 2007, 03:53 AM

Have you tried running it through MPLABs simulator. Should be easy to spot what's happening then.

Also try looking into the fcall macro

Code:

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

Suraj143 · 17th September 2007, 04:29 AM

Quote:

Originally Posted by blueroomelectronics

Have you tried running it through MPLABs simulator. Should be easy to spot what's happening then.

Hi blueroomelectronics thanks for your input.I have never used MPLAB simulator I dont know how to do that.

But when I reduced the data in the Table11 its working because its below first 0FFh mark.

And I dont know anything about macros.

bananasiong · 17th September 2007, 04:32 AM

Hi,
I think your table 12 should be working well.
Look at the table 11, it starts at memory location 0x00EC and ends at 0x010A. So you are able to call table 11 until 0x00ff. From 0x0100 onwards, it starts going wrong because the high side of table 11 is always 0x00.
Do you get what I mean?
You can force the high side of table 11 to start at 0x01 by:

Code:

   org 0x0100
table11
   addwf   PCL, f
.
.

Suraj143 · 17th September 2007, 04:52 AM

Quote:

Originally Posted by bananasiong

Hi,
I think your table 12 should be working well.
Look at the table 11, it starts at memory location 0x00EC and ends at 0x010A. So you are able to call table 11 until 0x00ff. From 0x0100 onwards, it starts going wrong because the high side of table 11 is always 0x00.
Do you get what I mean?

You are absolutely correct. When I reduced the data in the Table11 its starts working but when I add more data to Table11 its starts going wrong.

I’ll add org 0X0100 to Table11 as you mentioned

Code:

	org	0x0100
Table11	addwf	PCL,F
	retle	xx

And I’ll call the table like this from anywhere in my program memory like this.

Code:

	movlw	HIGH Table11
        movwf	PCLATH      
        call	Table11

Earlier I add org 0ECh to Table11 It also didn't fixed.Now only I understood the cut off mark is 100h.

Tell me am I right?

blueroomelectronics · 17th September 2007, 04:54 AM

Using the sim is simply selecting it from the debug menu. Add view watchlists like PCL and PCLATH and single step through your program.

bananasiong · 17th September 2007, 04:58 AM

Yes you're right. Because PCL is an 8-bit register. As long as the high side of the table doesn't change in the table, then everything will be fine.

Suraj143 · 17th September 2007, 05:07 AM

Thanks a lot bananasiong then for the Table12 I wont need an org statement.

I can call directly like this from anywhere in the program memory.

Code:

	movlw	HIGH Table12
        movwf	PCLATH      
        call	Table12

But if I add more tables after Table11 (100h) I have to look what Table exceeds the next 0FFh mark.

Suraj143 · 17th September 2007, 05:16 AM

Quote:

Originally Posted by blueroomelectronics

Using the sim is simply selecting it from the debug menu. Add view watchlists like PCL and PCLATH and single step through your program.

Hi blueroomelectronics as soon I'm going to try your simulating method.Thanks for that.

Pommie · 17th September 2007, 05:38 AM

If you calculate the address properly then you can have your tables anywhere you like.

Code:

TableNN
	movwf	Temp		;Save W
	movlw	High TabNN	;get high byte of address
	movwf	PCLATH		;put in PCLATH
	movlw	Low TabNN	;get low byte
	addwf	Temp,W		;add on offset
	btfsc	STATUS,C	;crossed page boundary?
	incf	PCLATH,F	;yes, so increment high byte
	movwf	PCL		;do jump

TabNN	dt	"Hello World",0

Mike.

Suraj143 · 17th September 2007, 05:49 AM

Hi Mike you are always there.

Oh I see another method.So I can place the Tables anywhere in the program memory.

In your method do I need to add org statements for Tables?Or without org statements I can place Tables anywhere?

Thanks.

Pommie · 17th September 2007, 05:59 AM

You can place tables anywhere, even if they cross a page boundary it will still work correctly.

Mike.

Suraj143 · 17th September 2007, 06:09 AM

Quote:

Originally Posted by Pommie

You can place tables anywhere, even if they cross a page boundary it will still work correctly.

Mike.

Thank you very much Mike for your support.

donniedj · 17th September 2007, 07:01 AM

Besides the giving of fish, good to also train how to fish.

AN556
http://ww1.microchip.com/downloads/e...tes/00556e.pdf

AN's - The great solvers of mystery.

eblc1388 · 17th September 2007, 07:53 AM

Anyone into PIC programming should really take time to fully understand the purpose and significance of PCLATH.

One would need to take care of it during Table read crossing 256 page boundary, CALL/GOTO code crossing 2K boundary and possibly interrupt handling.

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17th September 2007, 03:53 AM	(permalink)
blueroomelectronics	Have you tried running it through MPLABs simulator. Should be easy to spot what's happening then. Also try looking into the fcall macro Code: fcall macro subroutine_name local here lcall subroutine_name pagesel here here: endm __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com Last edited by blueroomelectronics; 17th September 2007 at 04:22 AM.

17th September 2007, 04:32 AM	(permalink)
bananasiong	Hi, I think your table 12 should be working well. Look at the table 11, it starts at memory location 0x00EC and ends at 0x010A. So you are able to call table 11 until 0x00ff. From 0x0100 onwards, it starts going wrong because the high side of table 11 is always 0x00. Do you get what I mean? You can force the high side of table 11 to start at 0x01 by: Code: org 0x0100 table11 addwf PCL, f . . __________________ Superman returns..

17th September 2007, 04:54 AM	(permalink)
blueroomelectronics	Using the sim is simply selecting it from the debug menu. Add view watchlists like PCL and PCLATH and single step through your program. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

17th September 2007, 04:58 AM	(permalink)
bananasiong	Yes you're right. Because PCL is an 8-bit register. As long as the high side of the table doesn't change in the table, then everything will be fine. __________________ Superman returns..

17th September 2007, 05:07 AM	(permalink)
Suraj143	Thanks a lot bananasiong then for the Table12 I wont need an org statement. I can call directly like this from anywhere in the program memory. Code: movlw HIGH Table12 movwf PCLATH call Table12 But if I add more tables after Table11 (100h) I have to look what Table exceeds the next 0FFh mark.

17th September 2007, 05:49 AM	(permalink)
Suraj143	Hi Mike you are always there. Oh I see another method.So I can place the Tables anywhere in the program memory. In your method do I need to add org statements for Tables?Or without org statements I can place Tables anywhere? Thanks.

17th September 2007, 05:59 AM	(permalink)
Pommie	You can place tables anywhere, even if they cross a page boundary it will still work correctly. Mike.

17th September 2007, 07:01 AM	(permalink)
donniedj	Besides the giving of fish, good to also train how to fish. AN556 http://ww1.microchip.com/downloads/e...tes/00556e.pdf AN's - The great solvers of mystery.

17th September 2007, 07:53 AM	(permalink)
eblc1388	Anyone into PIC programming should really take time to fully understand the purpose and significance of PCLATH. One would need to take care of it during Table read crossing 256 page boundary, CALL/GOTO code crossing 2K boundary and possibly interrupt handling. __________________ L.Chung