General Description
Introduction
The low-cost MC68HC05K3 microcontroller (MCU) is a member of the M68HC05 Family of microprocessors. This device has 64 bytes of user RAM, 128 bits of personality electronically erasable programmable ROM (PEEPROM), and 928 bytes of user ROM. This device is available in the 16-pin plastic dual in-line package (PDIP), 16-pin small outline integrated circuit (SOIC) package, and 20-pin super small outline
(SSOP) package. A functional block diagram of the MC68HC05K3 is shown in Figure 1-4.

FEATUREs
• Low-cost HC05 core
• 16-pin PDIP, 16-pin SOIC package, or 20-pin SSOP
• 928 bytes of user ROM, including eight bytes of user vectors
• 64 bytes of user RAM
• Low-power operation at 1.8 V — VDD minimum (EEPROM read only)
• 128 bits of personality EEPROM (not memory mapped) programmed using CPU software or with on-chip serial programming ROM
• On-chip charge pump for in-circuit programming of the personality EEPROM at 2.7 to 5.5 Vdc
• 8-bit free-running timer
• 4-stage selectable real-time interrupt generator
• 10 bidirectional input/output (I/O) lines including:
   – 8-mA sink capability on four I/O pins (PA7–PA4)
   – Mask option for software programmable pulldowns on all I/O pins
   – Mask option for port interrupts on four I/O pins (PA3–PA0) (keyboard scan feature)
• IRQ interrupt hardware mask, flag bit, and request bit
• Mask option for sensitivity on IRQ interrupt (edge- and level-sensitive or edge-sensitive only)
• On-chip oscillator (mask options for crystal/ceramic resonator oscillator with internal 2-MΩ resistor and 2-pin or 3-pin resistor capacitor (RC) oscillator)
• Mask option for reduced startup delay time with RC oscillator options
• Mask option for computer operating properly (COP) watchdog system
• Power-saving stop mode and wait mode instructions
• Mask option to convert STOP instruction to halt mode
• Illegal address reset
• Internal steering diode and pullup resistor on RESET pin to VDD
• Internal RESET pin pulldown from COP watchdog and ILADR