CPU Control Module Theory of Operation
2 - 2 0070-10-0441 Passport 2®/Passport 2 LT™ Service Manual
2.1 CPU Control Module
Overview
This board has the main program and system controller for the Passport 2. It also contains
the Communications Coprocessor, PCMCIA interface, RTC, Audio, CRT/LCD controller,
Serial Channels and module bus interface connectors.
2.1.1 MPC860T Host CPU, U2
Device U2, is a MPC860T Microcontroller, which contains a PowerPC core, 32 bit address
and data bus, Memory Controller (8 banks), general purpose timers, System Integration Unit
(SIU), Multi-Level Interrupts, Communications Processor module, SPI port, 100 Mbit Ethernet
Controller, and a Dual PCMCIA interface. Clock oscillator Y1, 5 Mhz, is multiplied by the
MPC860T's PLL circuit to achieve the 45MHz for Passport 2. There are six serial channels,
of which five are used. Two are full RS-232 compliant and are used for external
communications: one is used for the Recorder module; one is used to connect to the
Instrument Radio; and one is used for the Audio Synthesizer which goes to the Keypad/
Display connector.
There are eight programmable chip select/wait state control groups, only six are used. They
are listed below.
The power-on reset to the microcontroller is generated by U14, MAX814L CPU Supervisor.
The signal generated is active low for 140ms. PORESET* is generated whenever both VCC
rises from 0 to 4.75 volts and the 3.3V rises from 0 to 2.75V. The PORESET* signal is
distributed to other components that require a power on reset by using a spoke distribution
with series resistors instead of a daisy chain to better balance the signal paths. The U1 CPLD
in turn generates a HRESET* signal and a buffered BRESET* signal that is used to reset all
external components that require a reset other than PORESET*.
All high speed clock signal and control lines have series terminating resistors to reduce EMI.
2.1.2 Serial Communications Channels
There are four serial communications channels called SCC's that are part of the MPC860T's
Communication Processor Module. The following describes the function of each of them.
SCC1 - This channel is assigned to external communication use. It is buffered (U49) to RS-
232 levels before connection to the docking connector which is part of the base station or
comm-port system. SCC1 will operate in the standard UART mode with all hardware control
lines available.
SCC2 - This channel is assigned to external communication use. It is buffered (U50) to RS-
232 levels before connection to the docking connector which is part of the base station or
comm-port system. SCC2 will operate in the standard UART mode with all hardware control
lines available.
SCC3 - This channel is assigned to the Instrument Radio on connector J15.
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