upd78f0134hgka1-9et-a Renesas Electronics Corporation., upd78f0134hgka1-9et-a Datasheet - Page 130

• Manufacturer Part Number: upd78f0134hgka1-9et-a
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

<R>
5.6 Time Required to Switch Between Internal Oscillation Clock and High-Speed System Clock
high-speed system clock.
are executed using the pre-switch clock after switching MCM0 (see Table 5-5).
speed system clock.
stopping.
130
Bit 0 (MCM0) of the main clock mode register (MCM) is used to switch between the internal oscillation clock and
In the actual switching operation, switching does not occur immediately after MCM0 rewrite; several instructions
Bit 1 (MCS) of MCM is used to judge that operation is performed using either the internal oscillation clock or high-
To stop the original clock after switching the clock, wait for the number of clocks shown in Table 5-5 before
Note Setting is prohibited for the (A1) grade products.
Caution To calculate the maximum time, set f
Remarks 1. PCC: Processor clock control register
PCC2
0
0
2. f
3. f
4. The maximum time is the number of clocks of the CPU clock before switching.
PCC1
PCC
0
0
XP
R
: Internal oscillation clock frequency
: High-speed system clock oscillation frequency
Table 5-5. Maximum Time Required to Switch
PCC0
0
1
Between Internal Oscillation Clock and High-Speed System Clock
f
f
XP
XP
/f
/2f
R
R
+ 1 clock
+ 1 clock
High-Speed System Clock
CHAPTER 5 CLOCK GENERATOR
Internal Oscillation
User’s Manual U16899EJ3V0UD
Note
R
= 120 kHz.
Time Required for Switching
2 clocks
2 clocks
Note
High-Speed System Clock
Internal Oscillation