Arduino Mega e SPI

Hello everyone
I should interfacing my Arduino Mega2560 mcp4921 with a DAC that uses the SPI.
I found on web a code arduino and I have made ??some changes to the case, but I simulated all with Proteus and does not really work the DAC.
I checked power of both devices but nothing to do

Can anyone help me?

Thanks in advance

I enclose the following code written

#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
#define INTERNAL1V1 2
#define INTERNAL2V56 3
#define INTERNAL 3

// Arduino Pin 10 13 11 12
// MCP4921 DAC SS SCK MOSI n/a
#include "SPI.h"
// ATmega328P ADC
int analogPin = 0; // analog input channel
// ADC analog input value
word sensorValue = 0; // equivalent to unsigned int
// Byte of data to output to DAC
byte data = 0;

int digitalPin=53;

void setup()
  //set pin(s) to input and output
  //pinMode(53, OUTPUT);
  SPI.begin(); // wake up the SPI bus.
  pinMode(analogPin, INPUT);
  analogReference(INTERNAL2V56); //For 1280 and 2560
  //pinMode(2, INPUT);

void loop() {
// read the value from the sensor:
sensorValue = analogRead(analogPin); // comment out this line to test DAC
// sensorValue = 0x0200; // 0x03FF = Vref, 0x0200 = 1/2 Vref
sensorValue = sensorValue << 2 ; // 10 bit ADC to 12-bit DAC word
// set SS pin low, beginning 16-bit (2 byte) data transfer to DAC
digitalWrite(digitalPin, LOW);
// send high byte
data = highByte(sensorValue);
data = 0b00001111 & data; // clear 4-bit command field (optional)
data = 0b00110000 | data; // 0=DACA, 0=buffered, 1=1x, 1=output enabledSpi.transfer(data); // alt: shiftOut(MOSI, SCK, MSBFIRST, data);
// send low byte
data = lowByte(sensorValue);
SPI.transfer(data); // alt: shiftOut(MOSI, SCK, MSBFIRST, data);
// set SS pin high, completing 16-bit transfer to DAC
digitalWrite(digitalPin, HIGH);

Was there a question?
What do your debug prints tell you is happening?

I must receive digital string from pc by serial port and shift it to a dac (via spi)

In proteus this skecth doesn't work, can you help me to doing this project?

thanks in advance!