Introduction
The MC68HC11EA9 and MC68HC711EA9 microcontroller units (MCUs) are high-performance members of the M68HC11 family of MCUs. The MC68HC(7)11EA9 MCUs have a multiplexed external address and data bus and are characterized by high speed and low power consumption. Their fully static design allows operation at frequencies from 3 MHz to dc. The addition of a phase-locked loop (PLL) frequency synthesizer to the timer circuitry further enhances low-power operation and allows the use of lower frequency crystals while maintaining a clock speed of up to 3 MHz.

FEATUREs
• M68HC11 CPU
• 512 Bytes RAM (Data Retained During Standby, by use of VSTBY)
• 12 Kbytes Mask-Programmed ROM or EPROM
• 512 Bytes Electrically Erasable Programmable ROM (EEPROM)
• PROG Mode Allows Use of Standard EPROM Programmer (27C256 Footprint)
• Multiplexed Address and Data Buses Reduce Pin Count
• Enhanced 16-Bit Timer with Four-Stage Programmable Prescaler
   — Three Input Capture (IC) Channels
   — Four Output Compare (OC) Channels
   — One Additional Channel, Selectable as Fourth IC or Fifth OC
• 8-Bit Pulse Accumulator
• Phase-Locked Loop (PLL) Frequency Synthesizer for Reduced Power Consumption
• Power Saving STOP and WAIT Modes
• Real-Time Interrupt Circuit
• Computer Operating Properly (COP) Watchdog Timer
• Clock Monitor Circuit
• Enhanced Asynchronous Nonreturn to Zero (NRZ) Serial Communications Interface (SCI)
• Eight-Channel 8-Bit Analog-to-Digital (A/D) Converter
• Five Input/Output (I/O) Ports (34 Pins)
   — Four Bidirectional I/O Ports (26 Pins)
   — One Fixed Input-Only Port (8 Pins)
• Two Alternate, Fixed Input-Only Pins (XIRQ pin/XPIN bit and IRQ pin/IPIN bit)
• Available in 52-Pin Plastic Leaded Chip Carrier (PLCC), 52-Pin Windowed Ceramic Leaded Chip
   Carrier (CLCC), and 56-Pin SDIP (0.070” Lead Spacing)