UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 202

• Manufacturer Part Number: UPD78F0838
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

200
(3) Example of setting procedure when stopping the internal high-speed oscillation clock
<3> Selecting the CPU clock division ratio (PCC register)
The internal high-speed oscillation clock can be stopped in the following two ways.
(a) To execute a STOP instruction
(b) To stop internal high-speed oscillation clock by setting RSTOP to 1
Caution Be sure to confirm that MCS = 1 or CLS = 1 when setting RSTOP to 1. In addition, stop
Executing the STOP instruction to set the STOP mode
Setting RSTOP to 1 and stopping the internal high-speed oscillation clock
<1> Setting of peripheral hardware
<2> Setting the X1 clock oscillation stabilization time after standby release
<3> Executing the STOP instruction
<1> Confirming the CPU clock status (PCC and MCM registers)
<2> Stopping the internal high-speed oscillation clock (RCM register)
When CSS is cleared to 0, the main system clock is supplied to the CPU. To select the CPU clock
division ratio, use PCC0, PCC1, and PCC2.
CSS
Stop peripheral hardware that cannot be used in the STOP mode (for peripheral hardware that
cannot be used in STOP mode, see CHAPTER 20 STANDBY FUNCTION).
When the CPU is operating on the X1 clock, set the value of the OSTS register before the STOP
instruction is executed.
When the STOP instruction is executed, the system is placed in the STOP mode and internal high-
speed oscillation clock is stopped.
Confirm with CLS and MCS that the CPU is operating on a clock other than the internal high-speed
oscillation clock.
When CLS = 0 and MCS = 0, the internal high-speed oscillation clock is supplied to the CPU, so
change the CPU clock to the high-speed system clock or subsystem clock.
When RSTOP is set to 1, internal high-speed oscillation clock is stopped.
peripheral hardware that is operating on the internal high-speed oscillation clock.
0
CLS
0
0
1
PCC2
0
0
0
0
1
MCS
Other than above
0
1
×
PCC1
Preliminary User’s Manual U19748EJ1V0UD
CHAPTER 5 CLOCK GENERATOR
0
0
1
1
0
Internal high-speed oscillation clock
High-speed system clock
Subsystem clock
PCC0
0
1
0
1
0
f
f
f
f
f
Setting prohibited
MAIN
MAIN
MAIN
MAIN
MAIN
/2 (default)
/2
/2
/2
2
3
4
CPU Clock Status
CPU Clock (f
CPU
) Selection