Central Processing Unit (Cpu) - Honeywell Bendix/King KX 165A Maintenance Manual

BENDIX/KING KX 165A
4.2.5

CENTRAL PROCESSING UNIT (CPU)

The CPU controls the function of the unit and its connections can be seen in figure 4-8. An exter-
nal crystal sets the clock frequency for the CPU. The CPU also communicates to a RS-232 IC
that converts the CPU levels to those that are RS-232 compatible. An electronically erasable pro-
grammable read-only-memory device (EEPROM) is used to store alignment information and other
configuration data. The flash memory is used to store the unit software and the static random ac-
cess memory (SRAM) is used to supplement CPU memory. DME I/O conditions signals from the
CPU so they can be used to channel external DME equipment. Discrete I/O pass through filter
networks and switch transistors are then routed to the CPU for control purposes. A voltage mon-
itor on the 5V controls the reset line to the microprocessor, when the voltage on the 5V line is be-
low 4.75 VDC the CPU is held in the reset state.
Rev 0, Jun/2000 15610M00.RCD Page 4-21