Function And Operation Of Clock Generator - NEC PD754144 User Manual

6.2.2 Function and operation of clock generator

The clock generator generates the following types of clocks and controls the operation mode of the CPU in the
standby mode.
• System clock f
X
Φ
• CPU clock
• Clock to peripheral hardware
The operation of the clock generator is determined by the processor clock control register (PCC) as follows.
(a) When the RESET signal is asserted, the slowest mode of the system clock
(b) The CPU clock can be changed in four steps
(c) Two standby modes, STOP and HALT, can be used.
(d) The system clock is divided and supplied to the peripheral hardware units.
Notes 1. µ PD754144: 64 µ s at f
µ PD754244: 15.3 µ s at f
2. µ PD754144: 4, 8, 16, 64 µ s at f
µ PD754244: 0.95, 1.91, 3.81, 15.3 µ s at f
CHAPTER 6 PERIPHERAL HARDWARE FUNCTION
Note 2
by PCC.
= 1.0 MHz
CC
= 4.19 MHz, 10.7 µ s at 6.0 MHz
X
= 1.0 MHz
CC
0.67, 1.33, 6.67, 10.7 µ s at f
User's Manual U10676EJ3V0UM
Note 1
= 4.19 MHz
X
= 6.0 MHz
X
is selected (PCC = 0).
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