Hi Nichole,

here is a routine I use to receive the SHIFTOUT-ed data from the other
end.

' This program receives a binary byte sent by SHIFTOUT (MSB first)
' and displays it as decimal value on three 7-segment LED display.
' The order is 100, 10, 1, i. e. ones send first.
' They are driven by three daisy-chained 74164 ICs. The data
' coming by another shiftout. The input Clock is RB.0, input Data
' is RB.1
' As a special feature, a timeout for spurious clock pulses is
' also implemented.
' The transparent mode flag is always on, and a rescaling will be taken.
'   DEVICE  16C622

DEFINE  OSC     16

RCVD    VAR     BYTE    'the byte received
RDY     VAR     PORTB.2 'the Ready Flag
DIN     VAR     PORTB.1 'DATA_IN
CLK     VAR     PORTB.0
RDYLED  VAR     PORTA.4 'the Ready LED
DP100   VAR     PORTA.2
DP10    VAR     PORTA.1
DP1     VAR     PORTA.0
TRNP    VAR     PORTB.3 'Transparent Mode flag
COUT    VAR     PORTB.6
DOUT    VAR     PORTB.7

TEMP    VAR     BYTE    'temporary for EMIT
CTR     VAR     BYTE    'the bit counter
TEMPW   VAR     WORD    'temporary rescaled value
em_1    var     byte    'byte to be shift out

INCLUDE "modedefs.bas"

OPTION_REG = %11000100  'TMR0 prescaled w/32 = 3.2 msec at 10 MHz

TRISB.2 = 0             'Ready Flag as Output
RDY = 1                 'at start not ready
CMCON = %00000111       'turn all comparators off (622)
TRISA = %11101000       'Ready Led & DP's as Output
PORTA = 0               'D.P. test

EM_1 = 0                'full zero: '8'
GOSUB Emit_3
PAUSE 250
PORTA =  %00000111      'clear D.P.'s
EM_1 = $3               '0'
GOSUB Emit_3

MainLoop:
ASM
        bcf     _RDY
        bcf     _RDYLED
        movlw   8               ; prepare receive routine
        movwf   _CTR
ClkWait                         ; main receiving routine
        ClrWdt
        btfss   _CLK            ; Wait for Clock
        goto    ClkWait

        clrf    TMR0
        bsf     _RDY            ; receiving begun
        bsf     _RDYLED
        goto    Rcvr

ClkLo   btfsc   _CLK            ; Wait for Clock
        goto    Rcvr            ; CLKHI received
        movf    TMR0,W          ; check for TimeOut
        andlw   80h             ; overflow test
        btfss   STATUS.Z        ; skip if zero
        goto    _MainLoop
        goto    ClkLo

Rcvr    bcf     STATUS.C        ; clear carry
        btfsc   _DIN            ; copy DIN into Cy
        bsf     STATUS.C
        rlf     _RCVD           ; into Received
ClkHi   btfsc   _CLK            ; now wait for Clock low
        goto    ClkHi           ; no Wdt needed!
        decfsz  _CTR            ; loop
        goto    ClkLo
ENDASM

--------[cut here]------------

The result is now in _RCVD

I made a h/w handshake to signal the sender I'm ready to receive: it is
the _RDY line.


Cheers,
Imre


On Fri, 19 Jun 1998, <Nichole Petty> wrote:

> Hi everyone,
>
> I want to interface a BS2 to a PIC 16f84 via the BS2 shiftin/out command,
> using a clock to synchronize bit transfer. I have used the BS2 to talk to a/d
> converters and other using SPI interface. Now I want to create a PIC assembly
> routine that can be on the receiving end.
>
> Does anyone have some SPI or similar source code that shows how to do this?
>
> I have asked before with no luck, it must be regarded as "precious". I know
> the BS2 pulses the clock line for 14us then waits 46us for the next pulse. The
> clock pulses are used to synchronize the bit transfer. I haven't found
> anything on the web.
>
> Any help or direction appreciated.
>
>