UPD75238GJ NEC [NEC], UPD75238GJ Datasheet - Page 55
Manufacturer Part Number
4 BIT SINGLE-CHIP MICROCOMPUTER
The subsystem clock oscillator operates with a crystal resonator (32.768 kHz standard) connected to the
XT1 and XT2 pins.
An external clock can also be input.
Fig. 4-18 External Circuitry for the Subsystem Clock Oscillator
(a) Crystal oscillation
Caution When the main system clock or subsystem clock oscillator is used, conform to the following
guidelines when wiring at the shaded portions of Fig. 4-17 and 4-18 to eliminate the influence
of the wiring capacity.
• The wiring must be as short as possible.
• Other signal lines must not run in these areas. Any line carrying a high fluctuating current
must be kept away as far as possible.
• The grounding point of the capacitor of the oscillator must have the same potential as that
. It must not be grounded to ground patterns carrying a large current.
• No signal must be taken from the oscillator.
When the subsystem clock is used, pay special attention to its wiring; the subsystem clock
oscillator has low amplification to minimize current consumption and is more likely to malfunc-
tion due to noise than the main system clock oscillator.
(b) External clock