SPI program debugging HELP me plz..

Using Arduino Networking, Protocols, and Devices
2

If you want to write to that register, bit 7 of the register address must be set HIGH.

void writeRegister(byte thisRegister, byte thisValue) {

  digitalWrite(slaveSelect, LOW);

  // set bit 7 HIGH
  byte thisReg = thisRegister | 0x80;

  SPI.transfer(thisReg);
  SPI.transfer(thisValue);
  digitalWrite(slaveSelect, HIGH);
}

That is from page 16 on the datasheet.

edit: My bad! It is the other way around. Bit 7 is set HIGH for read and LOW for write. That is kinda backwards. The code above is for reading the register. :-[

You are just setting that register to its default value, so nothing will change by setting the configuration register to 0x0. Try this code. It sets the register to zero, reads the register, waits half a second, sets the register to one, then reads the register again. Every second you should see:
Register 0: 0
Register 1: 1

#include<SPI.h>

const byte address = 0b00000000;
const byte data = 0b00000000;
const int slaveSelect = 53;

void setup() {
  Serial.begin(9600);
  pinMode(slaveSelect, OUTPUT);
  SPI.begin();
}

void loop() {
  writeRegister(address, 0x00);
  rtnVal = readRegister(address);
  Serial.print(F("Register 0: "));
  Serial.println(rtnVal);
  delay(500);

  writeRegister(address, 0x01);
  rtnVal = readRegister(address);
  Serial.print(F("Register 1: "));
  Serial.println(rtnVal);
  delay(500);
}

void writeRegister(byte thisRegister, byte thisValue) {
  digitalWrite(slaveSelect, LOW);
  SPI.transfer(thisRegister);
  SPI.transfer(thisValue);
  digitalWrite(slaveSelect, HIGH);
}

byte readRegister(byte thisRegister) {
  digitalWrite(slaveSelect, LOW);

  byte thisReg = thisRegister | 0x80;

  SPI.transfer(thisRegister);
  regVal = SPI.transfer(0x0);
  digitalWrite(slaveSelect, HIGH);
  return(regVal);
}

Note I also changed the SPI setup to MSBFIRST (default). LSBFIRST bit order is incorrect for that device.