UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 200

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

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(4) Example of setting procedure when stopping the high-speed system clock
The high-speed system clock can be stopped in the following two ways.
(a) To execute a STOP instruction
(b) To stop X1 oscillation (disabling external clock input) by setting MSTOP to 1
Executing the STOP instruction and stopping the X1 oscillation (disabling clock input if the external clock is
used)
Setting MSTOP to 1 and stopping the X1 oscillation (disabling clock input if the external clock is used)
<1> Setting to stop 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 high-speed system clock (MOC register)
Caution Be sure to confirm that MCS = 0 or CLS = 1 when setting MSTOP to 1. In addition, stop
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 X1 oscillation
is stopped (the input of the external clock is disabled).
Confirm with CLS and MCS that the CPU is operating on a clock other than the high-speed system
clock.
When CLS = 0 and MCS = 1, the high-speed system clock is supplied to the CPU, so change the
CPU clock to the subsystem clock or internal high-speed oscillation clock.
When MSTOP is set to 1, X1 oscillation is stopped (the input of the external clock is disabled).
CLS
peripheral hardware that is operating on the high-speed system clock.
0
0
1
MCS
0
1
Preliminary User’s Manual U19748EJ1V0UD
CHAPTER 5 CLOCK GENERATOR
Internal high-speed oscillation clock
High-speed system clock
Subsystem clock
CPU Clock Status