upd78f0124m6gba1-8et Renesas Electronics Corporation., upd78f0124m6gba1-8et Datasheet - Page 123

• Manufacturer Part Number: upd78f0124m6gba1-8et
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

5.6 Time Required to Switch Between Internal Oscillation Clock and X1 Input Clock
X1 input clock.
are executed using the pre-switch clock after switching MCM0 (see Table 5-5).
input clock.
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 X1
To stop the original clock after switching the clock, wait for the number of clocks shown in Table 5-5.
Table 5-5. Maximum Time Required to Switch Between Internal Oscillation Clock and X1 Input Clock
Note Setting is prohibited for the (A1) and (A2) 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
XP
R
: Internal oscillation clock frequency
0
0
: X1 input clock oscillation frequency
PCC0
0
1
CHAPTER 5 CLOCK GENERATOR
User’s Manual U16315EJ3V1UD
f
f
XP
XP
/f
/2f
R
R
+ 1 clock
X1 → Internal Oscillation
+ 1 clock
Note
Time Required for Switching
R
= 120 kHz.
2 clocks
2 clocks
Internal Oscillation → X1
Note
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