UPD78F1502AGK-GAK-AX Datasheet, PDF (222/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
CHAPTER 5 CLOCK GENERATOR
CHAPTER 5 CLOCK GENERATOR
5.1 Functions of Clock Generator
The clock generator generates the clock to be supplied to the CPU and peripheral hardware.
The following three kinds of system clocks and clock oscillators are selectable.
(1) Main system clock
<1> X1 oscillator
This circuit oscillates a clock of fX = 2 to 20 MHz by connecting a resonator to X1 and X2.
Oscillation can be stopped by executing the STOP instruction or setting of MSTOP (bit 7 of the clock
operation status control register (CSC)).
<2> Internal high-speed oscillator ^Note
This circuit oscillates clocks of fIH = 1 MHz (TYP.) or fIH = 8 MHz (TYP.). After a reset release, the CPU
always starts operating with this internal high-speed oscillation clock. Oscillation can be stopped by
executing the STOP instruction or setting HIOSTOP (bit 0 of CSC).
<3> 20 MHz internal high-speed oscillation clock oscillator^Note
This circuit oscillates a clock of fIH20 = 20 MHz (TYP.). Oscillation can be started by setting bit 0 (DSCON) of
the 20 MHz internal high-speed oscillation control register (DSCCTL) to 1 with VDD ≥ 2.7 V. Oscillation can
be stopped by setting DSCON to 0.
Note To use the internal high-speed oscillation clock, use the option byte to set the frequency (1 MHz, 8
MHz, or 20 MHz) in advance (for details, see CHAPTER 26 OPTION BYTE). Also, the internal high-
speed oscillator automatically starts oscillating after reset release. To use the 20 MHz internal high-
speed oscillator to operate the microcontroller, oscillation is started by setting bit 0 (DSCON) of the 20
MHz internal high-speed oscillation control register (DSCCTL) to 1.
An external main system clock (fEX = 2 to 20 MHz) can also be supplied from the EXCLK/X2/P122 pin. An external
main system clock input can be disabled by executing the STOP instruction or setting of MSTOP.
As the main system clock, a high-speed system clock (X1 clock or external main system clock) or internal high-
speed oscillation clock can be selected by setting of MCM0 (bit 4 of the system clock control register (CKC)).
Remark
fX: X1 clock oscillation frequency
fIH: Internal high-speed oscillation clock frequency
fIH20: 20 MHz internal high-speed oscillation clock frequency
fEX: External main system clock frequency
R01UH0004EJ0501 Rev.5.01
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Jun 20, 2011