Kenwood TKR-740 Service Manual page 38

TKR-740
5.2 Sub CPU
The sub CPU (IC18) is of the same type as the main CPU,
but is programmed so that it operates as the sub CPU by
connecting its pin 18 to GND (pin 18 of the main CPU is
connected to Vdd.). The sub CPU functions as an I/O expander,
and controls the flash ROM , DSP, and extended I/O. IC15 and
IC16 are data bus buffer ICs.
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CIRCUIT DESCRIPTION
Fig.22 Sub CPU