Motorola MC68HC11 Microcontroller

The **MC68HC11** is an **8-bit microcontroller** developed by **Motorola** (later Freescale, now NXP). It is widely used in **automotive, industrial, and embedded systems** due to its rich set of **peripherals, ROM, RAM, EEPROM, and I/O support**.

Architecture Overview

• 8-bit CPU with **enhanced 6800 architecture**
• Harvard architecture with **separate program and data memory**
• Register-based execution with **indexed addressing modes**
• On-chip **oscillator and clock generation**
• Various power-saving modes

Memory and Storage

• **ROM**: 4 KB to 64 KB (varies by model)
• **RAM**: 256 B to 1 KB
• **EEPROM**: 512 B to 1 KB
• **Memory-mapped I/O** for peripherals

Peripherals and Features

• **GPIO (General Purpose I/O)** – Up to 40 pins
• **Timer System** – 16-bit timers with input capture/output compare
• **ADC (Analog-to-Digital Converter)** – 8-bit resolution
• **PWM (Pulse Width Modulation)** – Multiple channels
• **SCI (Serial Communication Interface)** – UART-based serial communication
• **SPI (Serial Peripheral Interface)** – Supports synchronous communication
• **I²C (Inter-Integrated Circuit)** – Compatible with multiple devices
• **Watchdog Timer (COP)** – Prevents system hang-ups

MC68HC11 Variants

Programming the MC68HC11

The MC68HC11 can be programmed using **assembly language, C, and BASIC**.

1. Assembly Language Example

Simple program to toggle an LED connected to **PORTB**:

ORG $1000
START:
    LDAA #$FF       ; Load A with 0xFF
    STAA PORTB      ; Output to PORTB (turn LED on)
    JSR DELAY       ; Delay
    CLRA            ; Clear A (0x00)
    STAA PORTB      ; Output to PORTB (turn LED off)
    JSR DELAY       ; Delay
    JMP START       ; Repeat
DELAY:
    LDX #$FFFF      ; Load X with max count
WAIT:
    DEX             ; Decrement X
    BNE WAIT        ; Loop until X = 0
    RTS             ; Return
        

2. C Programming with GCC

Basic **C program** to toggle an LED on **PORTB**:

#include <mc68hc11.h>
void delay() {
    volatile int i;
    for(i = 0; i < 50000; i++);
}
int main() {
    DDRB = 0xFF;  // Set PORTB as output
    while(1) {
        PORTB = 0xFF; // LED ON
        delay();
        PORTB = 0x00; // LED OFF
        delay();
    }
    return 0;
}