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Chapter 8
Clock Generator
Preliminary User’s Manual U14913EE1V0UM00
8.4 Control
Registers
8.4.1 Clock Control Register (CKC)
This is a 8-bit register that controls the clock management.
Data can be written to it only in a sequence of specific instructions so that its contents are not easily
rewritten in case of program hang-up.
This register can be read or written in 8- or 1-bit units.
Caution: Data is set to the registers by the following sequence:
1. Write the set data to the command register (PHCMD) (see Chapter 3.5 “Specific
2. Write the set data to the destination register (CKC)
To write data to the CKC register, use the store instruction (ST/SST) and bit manipulation instruction
(SET1/CLR1/NOT1).
The contents of this register can be read in the normal sequence.
7
6
5
4
3
2
1
0
Address
R/W
At Reset
CKC
PLLEN
0
TBCS
CESEL
0
0
0
0
FFFFF822H
R/W
00H
Bit name
Function
PLLEN
PLLEN enable bit
This bit enables or disables PLL operation.
0: PLL disabled
1: PLL enabled
Remark:
PLL is enabled when “1” is written to this bit. Passing stabilization time and synchro-
nization stage PLL output is used for system clock.
CESEL
Clock selection bit (X1,X2 pin function)
This bit sets PLL for proper operation with resonator or external oscillator.
0: Oscillation is enabled for a resonator
1: Oscillation is disabled
Note
Note:
If direct mode is selected by CLKSEL pin = 1, CESEL must be set to 1 by software after
RESET.
Remark:
If CESEL is set to 1, oscillator stabilization stage will be skipped whenever power
save mode is released by any interrupt or NMI request.
TBCS
Time base counter selection
This bit sets the clock source for the time base counter which is used to ensure the oscillator sta-
bilization time after software STOP mode has been released by any interrupt or NMI request, and
Flash stabilization time after the watch mode has been released.
In OSC mode (CESEL = 0):
TBCS
fxx = 4 MHz
fxx = 5 MHz
0
12.5 ms
10 ms
1
25 ms
20 ms
In direct mode (CESEL = 1):
TBCS
fxx = 4 MHz
fxx = 5 MHz
0
1.25 ms
1 ms
1
2.5 ms
2 ms
fxx: external oscillator frequency (clocking frequency / 2)
Remark:
If CESEL is set to 1, oscillator stabilization stage will be skipped whenever power
save mode is released by any interrupt or NMI request.
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