HD404054 Datasheet, PDF (30/101 Pages) Hitachi Semiconductor – HMCS400-series microcomputers designed to increase program productivity with large-capacity memory

HD404054 Series/HD404094 Series
Internal Oscillator Circuit
A block diagram of the clock generation circuit is shown in figure 17. As shown in table 18, a ceramic
oscillator can be connected to OSC₁ and OSC₂. The system oscillator can also be operated by an external
clock.
After RESET input or after stop mode has been cancelled, the division ratio of the system clock can be
selected as 1/4 or 1/32 by setting the SEL pin level.
• 1/4 division ratio: Connect SEL to V_CC.
• 1/32 division ratio: Connect SEL to GND.
OSC₂
OSC₁
System ^{fOSC 1/4 or fcyc} Timing
oscillator
1/32
division
t_cyc
generator
circuit
circuit*
φ_CPU
φ_PER
Note: * 1/4 or 1/32 division ratio can be selected by SEL pin.
Figure 17 Clock Generation Circuit
CPU with ROM,
RAM, registers,
flags, and I/O
Peripheral
function
interrupt
RE₀
TEST
OSC₁
OSC₂
RESET
GND
GND
Figure 18 Typical Layout of Ceramic Oscillator
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