-Andy wrote:
>
> Come on, Henri... Assembly-language programming doesn't get much easier
> than this.
Ohh. Shame on me :-)
But I mostly end up with some optimized code from some "AN..." of the
Embedded Control Handbook". So I like to see something good. And two
persons (mostly) have two different ideas. So I could already catch
some good idea from your code. Thanks for that.
>
> Since you didn't give any details, I'll assume that DATA is valid when
> SCLK is high, and that you're only reading 8 bits from the interface.
>
Well, I didn't want bother you all to much. So I reduced the problem
to a small kernel.
Actually I have to interface an ADC AD7714 to a PIC hostcontroller.
Things get a little bit easier when I (e.g. the PIC) provide the
SCLK. BTW: it's also a 3-wire interface, but that doesn't make a
difference in general. I have to send lots of control data to the
ADC, then initiate a read-cycle, then read 16/24bit of data.
Then I'll do just something with that conversion data I hopefully get.
But plenties of time probably will walk throu the land before I get
this far.

Bye
           Henri

--

>         #DEFINE DATA    [any port]
>         #DEFINE SCLK    [any other port]
>
>         RECEIVE EQU     [any file register]
>
>         ;.... initialize registers, setup port TRIS registers, etc. ....
>
>         GETBYTE MOVLW   00000001B       ;PUT A "1" IN "RECEIVE"'S LSB SO
>                 MOVWF   RECEIVE         ;WE'LL KNOW WHEN WE'VE RECEIVED
>                                         ;8 BITS.
>
>                 CLRC                    ;ASSUME WE'LL SHIFT A "0" INTO
>                                         ;"RECEIVE".
>
>         GETBIT  BTFSS   SCLK            ;WAIT FOR SCLK TO GO HIGH (CARRY
>                 GOTO    $-1             ;IS ALWAYS CLEAR HERE).
>
>                 BTFSC   DATA            ;IF DATA = 0, SKIP AHEAD.
>                 SETC                    ;OTHERWISE, SETUP TO SHIFT A
>                                         ;"1" INTO "RECEIVE".
>
>                 RLF     RECEIVE         ;SHIFT THE CARRY INTO "RECEIVE".
>
>                 SKPNC                   ;IF WE'VE RECEIVED ALL 8 BITS,
>                 GOTO    DONE            ;GO EXIT.
>
>                 BTFSC   SCLK            ;OTHERWISE, WAIT FOR SCLK TO GO
>                 GOTO    $-1             ;LOW.
>
>                 GOTO    GETBIT          ;LOOP BACK.
>
>         DONE    ....                    ;8 BITS OF RECEIVED DATA ARE IN
>                                         ;"RECEIVE".  FIRST BIT RECEIVED
>                                         ;IS IN THE MSB, LAST BIT IS IN
>                                         ;THE LSB.
>
> -Andy


--
=============> The sanest place is still behind the trigger <===============
[]-------------------------------[]---------------------------------------[]
||         Henri Schultze        || Magdeburg D-39122 Alt-Fermersleben 88 ||
||   henri@fscz-md.boerde.de     ||          The Cracker Company          ||
[]-------------------------------[]---------------------------------------[]
=================> in a world of compromise, some don't <===================