Zwei Schieberegister in Reihe: Denkfehler?

#include <htc.h>

__CONFIG(1, FCMDIS & IESODIS & HS);

__CONFIG(2, BORDIS & BORV45 & PWRTEN & WDTDIS & WDTPS1);

__CONFIG(3, CCP2RB3 & LPT1DIS & 0xFDFF);

__CONFIG(4, DEBUGDIS & XINSTDIS & LVPDIS & STVRDIS);

__CONFIG(5, 0xFFFF);

__CONFIG(6, 0xFFFF);

__CONFIG(7, 0xFFFF);

#define storage_reg       PORTCbits.RC2

//prototypes

void wait (unsigned int);

void showInt595(unsigned);

void main (void)

{

unsigned int uValue;

/***************************************************************

* 20.07.2011

* spi 74HC595 shift register test

*

* Lines for PIC 18F4550:

* clk: RB1, Pin34

* Ser out, (in for '595): RC7, Pin14

* /G (output enable): RC6 (mußt be low)

* storage register: RC2, Pin12

* RD2: /SCLR clear latch (testing...)

**************************************************************/

// port directions: 1=input, 0=output

  PORTB  = 0b00000000;  //clear output data latch

  TRISB  = 0b00000000;  //set to output

  PORTC  = 0b00000000;  //clear output data latch

  TRISC  = 0b00000000;  //set to output

  PORTD  = 0b00000000;  //clear output data latch

  TRISD  = 0b00000000;  //set to output

//while (1) {

PORTCbits.RC0=1; // Einschalt-LED

wait (300);

PORTCbits.RC0=0; // Einschalt-LED

//wait (300);

//}

  OpenSPI  (SPI_FOSC_64, MODE_10, SMPMID);

  showInt595(0x0001); 

  wait (300);

  showInt595(0x0002); 

  wait (300);

  showInt595(0x0004); 

  wait (300);

  while (1);

 } // Ende main

//wait

void wait(unsigned int a) {

  unsigned int i,j;

    for (i = 0; i < a ; i++) {

       for (j = 1 ; j < 1000; j++); 

      }

}

/***************************************************************

* 20.07.2011

* 

*

* precondition:

* Lines for PIC 18F4550 mußt be properly initialised

* clk: RB1, Pin34, Pin11 at '595 

* Ser out: RC7, Pin14 at '595

* free selectable: output storage register: RC2 Pin17, Pin12 at '595

*

* /G (output enable): Pin13 on gnd

* /SCLR (clear shift register) Pin10 on Vcc

* /Qh (Pin9) output to the next 595's serial in, input Pin14 

*

* 

**************************************************************/

void showInt595 (unsigned uPattern) 

{

  unsigned uDummy1,uDummy2; // = unsigned int

  unsigned char ucPattern;

  //'595 No1

  //die 16bit in 2x 8bit zerlegen, unteres Byte:

  uDummy1 = uPattern;

  uDummy1= uDummy1 & 0x00FF;

  uDummy1 = (unsigned char) uDummy1;  //ist das eigentlich erlaubt bzw. notwendig???

  ucPattern = uDummy1;  

  WriteSPI(ucPattern);

  //wait (1);           // PIG zu schnell...?

  //storage_reg = 1;    // würde zwar funktionieren, erzeugt aber

  //storage_reg  = 0;   // ein kurzes störendes Blitzen auf den 

                        // korrespondierenden 8 bits

  //'595 No2  

  //die 16bit in 2x 8bit zerlegen, oberes Byte:

  uDummy2 = uPattern;

  uDummy2 >>= 8;

  uDummy2 = (unsigned char) uDummy2;

  ucPattern = uDummy2;  

  WriteSPI(ucPattern);

  wait (1);           // PIG zu schnell...?

   storage_reg = 1;   // alle 16 bits ins Ausgaberegister 

   storage_reg = 0;   // wieder freigeben

}