Datasheet

Chapter 2 — Theory of Operation
6 PB42 Portable Receipt Printer Service Manual
Microprocessor
The microprocessor (U1) for the PB42 is the Freescale MPC875. The
following sections describe circuitry connected directly to the
microprocessor.
Power Supply Sequencing and Bypass Capacitors
Power Sequencing and Bypass Capacitors for U1
D101 helps keep VDD (1.8 V) from ever rising faster than the +3.3 V
supply (VCC). D102 is a 1.8 V zener. It keeps VCC and VDD from being
too far from each other.
There are five 0.1 μF ceramic bypass caps on each supply, two 10 μF
capacitors on VCC, and one 10 μF capacitor on VDD.
Clock Generation Circuitry
10MHz Crystal Circuit for the Internal Clock