+/**
+ * proof of concept for writing data to an SRAM with 
+ * 3 74HC595 shift registers and reading data out 
+ * via different Arduino Pins.
+**/
+
+
+//
+// pins used for the shiftout
+//
 #define CLOCK 4
 #define LATCH 3
 #define DATA  5
 
+//
+// pins used for write pulse of the SRAM 
+// and the output enable of the data-bus shift register
+//
 #define WR    2
 #define OEDATA 14
+
 
 void setup() {
  pinMode(CLOCK,OUTPUT); 

 Serial.begin(9600);
 delay(100);
 

 Serial.println("writing data");
 for (int i=0;i<=255;i++) {

    write2RAM(i,(byte)i);
 }
 
 // read back all 256 bytes
 Serial.println("reading data:");
 for (int i=0;i<=255;i++) {
    byte d = readRAM(i);
