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PEEP: Personality EEPROM
Mask ROM MCUs are typically lower in cost compared to OTP, EPROM, or EEPROM MCUs in high volume applications. OTP, EPROM, and EEPROM MCUs have the advantage of being able to customize each microcontroller whereas a mask ROM MCU must have the same code.

Personality EPROM (PEP) is a small block of EPROM organized serially that can be added to mask ROM MCUs. While more expensive than mask ROM parts, they are typically cheaper than all EPROM or OTP parts and retain the advantage of customization.

Personality EEPROM (PEEP) is identical in function to PEP except the EPROM is replaced by EEPROM.

Typical applications of PEP and PEEP include:

  • Storage of electronic I.D. (serial number)

  • RF security systems (remote car locks, home alarm, etc)

  • Configuration data

  • Increase reliability and lower cost by eliminating dip switches

  • Allow more user friendly set-up and use

  • Calibration data

  • Correct for system variation at manufacturing or in the field

PEP: Personality EPROM

PLL: Phase-Lock Loop
The phase-locked loop (PLL) is a frequency generator that takes an input clock frequency and multiples it to a much higher frequency. The 68HC08 has two different PLL modules, one uses a 32Khz crystal as its input and another uses a 1 - 4 Mhz crystal. Both versions generate the internal clocks used to support 8Mhz bus operation. Without the PLL, 68HC08s would require a 32Mhz oscillator which is expensive and can potentially generate unwanted noise in the MCU application. The

PWM: Pulse-Width Modulation
The pulse width modulate (PWM) mechanism is useful for generating signals to control motors, gauge drivers, switching power supplies, and low cost D/A converters. A typical D/A application would configure the PWM module to a generate a waveform with a fixed period and to set the duty cycle (the relative time the signal is high vs low) to specify the desired analog value.