Renesas RL78/F14 User Manual

RL78/F13, F14 CHAPTER 5 CLOCK GENERATOR
R01UH0368EJ0210 Rev.2.10 370
Dec 10, 2015
Figure 5-3. 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
Note 1
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
CKSEL
register
CMC register Subsystem clock pin operation
mode
XT1/P123 pin XT2/EXCLKS/
P124 pin
SELLOSC
Note 1, 2
EXCLKS OSCSELS
Note 1
x 0 0 Input port mode Input port
0 0 1 XT1 oscillation mode Crystal/ceramic resonator
connection
1 0 1 Input port mode (low-speed on-
chip oscillator operation mode)
Input port
x 1 0 Input port mode Input port
0 1 1 External clock input mode Input port External clock
input
1 1 1 Input port mode (low-speed on-
chip oscillator operation mode)
Input port
AMPHS1 AMPHS0 XT1 oscillator oscillation mode selection
Note 3
0 0 Low power consumption oscillation (default) Oscillation margin: Medium
0 1 Normal oscillation Oscillation margin: high
1 0 Ultra-low power consumption oscillation Oscillation margin: Low
1 1 Setting prohibited
AMPH Control of X1 clock oscillation frequency
0 1 MHz  fX  10 MHz
1 1 MHz  fX  20 MHz
Notes 1. The 20-, 30-, and 32-pin products do not have a subsystem clock (fSUB). If the low-speed on-
chip oscillator is selected as the source of the clock signal for the CPU/peripheral hardware
clock (fCLK) or for a peripheral function, set the SELLOSC bit to 1.
2. When the SELLOSC bit is set to 1, the subsystem clock (f
SUB) cannot be supplied to the input
clock (f
RTC) of the real-time clock.
3. As the XT oscillator becomes oscillation mode with lower power consumption, then its
oscillation margin becomes smaller.
Cautions 1. The CMC register can be written only once after reset release, by an 8-bit memory
manipulation instruction. When the CMC register is used at the default value (00H),
be sure to set 00H to this register after reset release in order to prevent
malfunctioning during a program loop.

Renesas RL78/F14 Specifications

General

Brand	Renesas
Model	RL78/F14
Category	Computer Hardware
Language	English