General Description
Introduction
The Motorola MC68HC05P18A is a low-cost microcontroller with:
   • 4-channel, 8-bit analog-to-digital (A/D) converter
   • 16-bit timer with output compare and input capture
   • Serial communications port (SIOP)
   • Computer operating properly (COP) watchdog timer
The HC05 central processor unit (CPU) core contains:
   • 192 bytes of random-access memory (RAM)
   • 8064 bytes of user read-only memory (ROM)
   • 128 bytes of electrically erasable programmable read-only memory (EEPROM)
   • 21 input/output (I/O) pins (20 bidirectional, 1 input-only)
This device is available in:
   • 28-pin plastic dual in-line package (PDIP)
   • 28 pin small-outline integrated circuit package (SOIC)
A functional block diagram of the MC68HC05P18A is shown in Figure 1-1.

FEATUREs
Features of the MC68HC05P18A include:
   • Low-cost, HC05 core running at 2-MHz bus speed, or the 4-MHz high-speed option
   • 28-pin DIP or SOIC package
   • On-chip crystal/ceramic resonator
   • 8064 bytes of user ROM including:
      – 48 bytes of page zero ROM
      – 16 bytes of user vectors
   • 192 bytes of on-chip RAM
   • 128 bytes of EEPROM
   • Low-voltage reset (LVR)
   • Four-channel, 8-bit A/D converter
   • Serial communications port
   • COP watchdog timer with active pull down on RESET
   • 16-bit timer with output compare and input capture
   • Edge- and level-sensitive interrupt or edge-sensitive only (mask option)
   • 20 bidirectional I/O lines and 1 input-only line
   • Individually mask selectable pullups/interrupts on port A pins
   • High current sink and source on two I/O pins, PC0 and PC1
   • Power-saving stop mode and wait mode instructions and stop conversion to halt mode (mask option)
   • Mask option for clock output pin