more than 8 bit for tables in flash (16F87x)

[BigWumpus]

Is there any way to store more than 8 bit (f.e. 10) in a 14-Bit-Word inside the flashmemory for tables ?

All MPASM-directives only allow 8 Bit.

[Acetronics2]

Hi, Wumpus

as we are in the PbP forum ... you could have a closer look to lookup2 and lookdown2 statements that deal with 16bits values ...
a look to WRITECODE or READCODE could be valuable too ...

That reminds me an old post from MEL about that subject ..." Playing with ... as a playground "
that one also : http://www.pbpgroup.com/modules/wfse...p?articleid=10

for MPASM exclusive use, two times the RETLW xx method seem to be unavoidable ... as W register is "only" 8 bits ...

Alain

[paul borgmeier]

All MPASM-directives only allow 8 Bit.

maybe I am mistaken, but I thought the MPASM DATA directive gave you full access to store 14 bit numbers in code space ... see DATA in MPASM help topics

Paul Borgmeier
Salt Lake City, Utah
USA

[BigWumpus]

READCODE ist used... it can read 14-Bit-Code into Word-Variables !
(Writecode too!)

But, you can't put 14-Bit-parameters in the flash.

With the 18F... it will work (DW 1234h)

I think somebody was pretty in love with the RETW-statement (or how else it is written).

[Darrel Taylor]

Like Ace said, LOOKUP2 will do the job, but it's a bit code heavy.

This is a variant of the Strings idea that allows Very Large 14-bit WORD sized tables in code space.

Address   VAR  WORD
DataWord  VAR  WORD
Offset    VAR  WORD

'-----------------------------------------------------------------------------
ASM
GetAddress macro Label, Wout       ; Returns the Address of a Label as a Word
    CHK?RP Wout
    movlw low Label
    movwf Wout
    movlw High Label
    movwf Wout + 1
    endm
ENDASM

'-----[The DATA table]--------------------------------------------------------
ASM
DataTable
    DW  1234h, 2178h
endasm

'-----[Retrieve from DATA table]----------------------------------------------
Offset = 1
@  GetAddress   DataTable, _Address
Address = Address + Offset
ReadCODE  Address, DataWord

LCDOUT  $FE, 1, HEX4 DataWord

[Darrel Taylor]

Or, if you only have One table to deal with, you could do it this way...

DataWord  VAR  WORD
Offset    VAR  WORD
DataTable CON  EXT

'-----[The DATA table]--------------------------------------------------------
ASM
DataTable
    DW  1234h, 2178h
endasm

'-----[Retrieve from DATA table]----------------------------------------------
Offset = 1
ReadCODE  (DataTable + Offset), DataWord

LCDOUT  $FE, 1, HEX4 DataWord

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[BigWumpus]

Hi Darrel,

Uuuuhhh......

DW is not working for PIC16F.... it places a WORD packed in 2 BYTEs with a RETLW added.

READCODE cannot adress the table direct, you have to use the macro, i guess. (but I will see what this CON EXT will be...)

LOOKDOWN2 is ... I don't use it. My routine looks like this:
;================================================= =========================
NTC2Temp:
@ SetI2CText _Tab_NTC
I=0 ;Anfangstemperatur der Tabelle
Gosub ReadWord ;Anfangsspannungswert ADC
While DummyW ;solange die Tabelle noch nicht durch ist
Dummy2W=DummyW:Gosub ReadWord
For J=1 to 5
If ADC_NTC<Dummy2W Then ;wenn Temperatur noch nicht gefunden
Dummy2W=Dummy2W-(Dummy2W-DummyW)/(6-J):I=I+1
Endif
Next J
Wend
Dummy=I:Return

;================================================= =========================
;Umrechnung NTC
;gemessener ADC-Wert auf Temperatur
Tab_NTC:
@ DW 879,852,821,786,747,704 ;0-25°C
@ DW 659,612,564,516,468,419 ;30-55°C
@ DW 375,338,303,270,239,211 ;60-85°C
@ DW 187,166,147,130,116,103 ;90-115°C
@ DW 92,82,73,65,58,52,47 ;120-150°C
@ DW 0

;================================================= =========================

the datapoints (every 5 degrees) must be interpolated, so LOOKDOWN2 is not realy good to me.

[Darrel Taylor]

DW is not working for PIC16F.... it places a WORD packed in 2 BYTEs with a RETLW added

I think you've got it backwards.
This is DW data compiled for a 16F877. It places each 14-bit word value in successive program word locations, which can then be read with READCODE.

0286                  00490 DataTable
0286   1234 2178 0001 00491     DW  1234h, 2178h, 0001h, 0781H
       0781

This is the same data used in a LOOKUP2 statement.

                      00516         LU2RET?C        01234h
0301   3434               M         retlw   low (01234h)
0302   3412               M         retlw   high (01234h)
0303   3400               M         retlw   0
                      00517         LU2RET?C        02178h
0304   3478               M         retlw   low (02178h)
0305   3421               M         retlw   high (02178h)
0306   3400               M         retlw   0
                      00518         LU2RET?C        001h
0307   3401               M         retlw   low (001h)
0308   3400               M         retlw   high (001h)
0309   3400               M         retlw   0
                      00519         LU2RET?C        00781h
030A   3481               M         retlw   low (00781h)
030B   3407               M         retlw   high (00781h)
030C   3400               M         retlw   0

It's the LOOKUP2 that puts the retlw's in there.

As for the examples above. I have run the code. It works.

You didn't include the ReadWord subroutine with your code so I can't tell how yours is tryng to read the NTC table.
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