Filter
Top Products
RL78/G1A CHAPTER 5 CLOCK GENERATOR
R01UH0305EJ0200 Rev.2.00 144
Jul 04, 2013
Figure 5-2. Format of Clock Operation Mode Control Register (CMC)
Address: FFFA0H After reset: 00H R/W
Symbol 7 6 5 4 3 2 1 0
CMC EXCLK OSCSEL EXCLKS OSCSELS 0 AMPHS1 AMPHS0 AMPH
EXCLK OSCSEL High-speed system clock
pin operation mode
X1/P121 pin X2/EXCLK/P122 pin
0 0 Input port mode Input port
0 1 X1 oscillation mode Crystal/ceramic resonator connection
1 0 Input port mode Input port
1 1 External clock input mode Input port External clock input
EXCLKS OSCSELS Subsystem clock pin
operation mode
XT1/P123 pin XT2/EXCLKS/P124 pin
0 0 Input port mode Input port
0 1 XT1 oscillation mode Crystal resonator connection
1 0 Input port mode Input port
1 1 External clock input mode Input port External clock input
AMPHS1 AMPHS0 XT1 oscillator oscillation mode selection
0 0 Low power consumption oscillation (default)
0 1 Normal oscillation
1 0 Ultra-low power consumption oscillation
1 1 Setting prohibited
AMPH Control of X1 clock oscillation frequency
0 1 MHz ≤ fX ≤ 10 MHz
1 10 MHz < fX ≤ 20 MHz
Cautions 1. The CMC register can be written only once after reset release, by an 8-bit memory
manipulation instruction. When using the CMC register with its initial value (00H), be
sure to set the register to 00H after a reset ends in order to prevent malfunction due
to a program loop. Such a malfunction becomes unrecoverable when a value other
than 00H is mistakenly written.
2. After reset release, set the CMC register before X1 or XT1 oscillation is started as set
by the clock operation status control register (CSC).
3. Be sure to set the AMPH bit to 1 if the X1 clock oscillation frequency exceeds 10 MHz.
4. Specify the settings for the AMPH, AMPHS1, and AMPHS0 bits while f
IH is selected as
fCLK after a reset ends (before fCLK is switched to fMX or fSUB).
5. Oscillation stabilization time of f
XT, counting on the software.
6. Although the maximum system clock frequency is 32 MHz, the maximum frequency
of the X1 oscillator is 20 MHz.
(Cautions and Remark are given on the next page.)