Hi.
For the MCR12 Clock pin you must use Arduino Uno R3 pins 2 or 3 (that are INT0 and INT1 pins), no others.
Use the PS2Keyboard library 2.4 PS2Keyboard Library, Connect a keyboard for user input
Try this sketch:
#include <PS2Keyboard.h>
const int DataPin = 3;
const int IRQpin = 2;
PS2Keyboard keyboard;
void setup() {
keyboard.begin(DataPin, IRQpin);
delay(1000);
Serial.begin(9600);
Serial.println("Keyboard Test:");
}
void loop() {
if (keyboard.available()) {
char c = keyboard.read();
if (c == PS2_ENTER) {
Serial.println();
} else {
Serial.print(c);
}
}
}