Hi,

Mike Blakey wrote:
>I am using a 16f876 and have a large lookup table of values, (196 bytes) At
present
>this table is in EEDATA. the access to the data is not quite fast enough, I
believe
>that it is possible to copy this data into program memory, possible using a
routine
>at boot-up. I have looked in Microchips archive, and don't fully understand
how to
>do this. Has anyone done this sort of thing before, and could point me in
the right
>direction,  Thanks.

From what I understand you are using the eeram to store the table ?
In that case I assume something like this is used to access it:

; ***********************************************************************
; EE_WRITE_BYTE - Routine to read a byte from ee ram
; Adress in W, byte will be delivered in W
EE_READ_BYTE
        BANK2
        MOVWF   EEADR           ; put in adress reg.
        BSF     STATUS,RP0      ; bank3 !!
        BCF     EECON1,EEPGD    ; set to read data memory
        BSF     EECON1,RD       ; set bit to read
        BCF     STATUS,RP0      ; bank2 !!
        MOVF    EEDATA,W        ; move data to W
        BANK0                   ; Reset to BANK0 !
        RETURN                  ; and return

Something around 12 instructions not counting the call/return, if
this is to 'slow' then there always is the program table path
which can be accomplished by somthing like:

GET_TABLE_BYTE
        ADDWF PCL
MY_TABLE
dt 0x01, 0x02, 0x03, 0x04,......

        IF ((HIGH ($)) != (HIGH (MY_TABLE)))
        ERROR "TABLE CROSSES PAGE BOUNDARY, RE-ALIGN !"
        ENDIF

Which would generate more or less only 1 instruction for the
same task. Which is as fast as you can go I'm afraid.
On the 16F876 one can always access the flash mem by similar
means as the eeram but it would only be something around
1-2 instructions shorter than the normal eeram read.
However it would 'save' program space if it would be
sufficient to save only 7 bits/variable.

see: http://www.piclist.com/techref/microchip/tables.htm
for additional info and pointers.
*beware* of program pages !

/Tony

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