Pic16f tables bigger than 256

P

pixman

Member

• May 18, 2010

• #1

Hi
i would like to know how you would set out tables if they are morre than 255
i have read that if you have tables, they should not cross the 255 mark.
I have a program that has 5 tables, the 5th table cross this 255 area and when
i use this table it does not work properly.

Help please
DAVID

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• May 18, 2010

• #2

Check my tutorials, particularly the 8x8 LED matrix one.

 

P

pixman

Member

• May 18, 2010

• #3

I HAD A LOOK AT THE 4 TUTORIALS.
IT STILL DOES NOT MAKE SENSE TO ME.
CAN I USE
org 0X100
AFTER TABLE 4 TO PUT IT IN A NEW 256 AREA

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• May 18, 2010

• #4

You can certain use ORG to place tables at specific places, and my earlier tutorials do that. But it's tutorial 13 that uses tables larger than 256 bytes.

 

M

Magen

New Member

• May 18, 2010

• #5

Hi Pixman,
https://www.electro-tech-online.com/custompdfs/2010/05/31006a.pdf
and
Microchip's AN556

should also be helpful.

 

blueroomelectronics

Well-Known Member

• May 18, 2010

• #6

If you need large tables the 18F PICs are much better suited.

 

C

colin55

Well-Known Member

• May 18, 2010

• #7

Place Table 5 at location 200h by using the instructions:
org 0x200
table5 addwf pcl,f
retlw .5
retlw 0ffh etc

in your main program, add:

movlw 02
movwf PCLATH
movlw jump value for table 5
call table5

 

P

pixman

Member

• May 18, 2010

• #8

Thanks for the help i will try it later

 

C

colin55

Well-Known Member

• May 18, 2010

• #9

Tables in baseline PIC chips can only be placed in the first 256 addresses of memory.

 

Last edited: May 18, 2010

Nigel Goodwin

Super Moderator

Most Helpful Member

• May 19, 2010

• #10

colin55 said:

Tables in baseline PIC chips can only be placed in the first 256 addresses of memory.

Click to expand...

16F (14 bit) series can go anywhere, are you refering to 12 bit devices?.

 

P

pixman

Member

• May 19, 2010

• #11

I will be using a 16f877a and 16f628a

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• May 19, 2010

• #12

pixman said:

I will be using a 16f877a and 16f628a

Click to expand...

They are fine, and covered in my tutorials.

 

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pixman

Member

• May 19, 2010

• #13

So would i be correct in saying that for 16f628a
start: 0x005
next : 0x200
0x400
0x600
end: 0x7ff
that is how you put tables in different places

and for the 16f877a the same would apply but continued for page 1 to page 3

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• May 19, 2010

• #14

It's one way, not forgetting to do the PCLATH switching as post #7.

Or you could use large tables, and ignore the switching - as my tutorial 13 does.

 

P

pixman

Member

• May 19, 2010

• #15

I have had a good look at tutorial 13 and i can't seem to figure it out.
I will play with it in mplab to see if i can understand what you did.

Thank you for your help

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• May 19, 2010

• #16

pixman said:

I have had a good look at tutorial 13 and i can't seem to figure it out.
I will play with it in mplab to see if i can understand what you did.

Click to expand...

You don't need to understand it, just cut out the part you need.

 

P

Pommie

Well-Known Member

Most Helpful Member

• May 19, 2010

• #17

Nigel Goodwin said:

You don't need to understand it, just cut out the part you need.

Click to expand...

But, it's much better if you do.

Mike.