upd78f0730 Renesas Electronics Corporation., upd78f0730 Datasheet - Page 111

• Manufacturer Part Number: upd78f0730
• Description: 8-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

5.6.8 Time required for switchover of CPU clock and main system clock
system clock can be changed.
pre-switchover clock for several clocks (see Table 5-6).
internal high-speed oscillation clock to the high-speed system clock).
pre-switchover clock for several clocks (see Table 5-7).
ascertained using bit 1 (MCS) of MCM.
5.6.9 Conditions before clock oscillation is stopped
conditions before the clock oscillation is stopped.
PCC2 PCC1 PCC0
Set Value Before
0
0
0
0
1
By setting bits 0 to 2 (PCC0 to PCC2) of the processor clock control register (PCC), the division ratio of the main
The actual switchover operation is not performed immediately after rewriting to PCC; operation continues on the
Remark The number of clocks listed in Table 5-6 is the number of CPU clocks before switchover.
By setting bit 0 (MCM0) of the main clock mode register (MCM), the main system clock can be switched (the
The actual switchover operation is not performed immediately after rewriting to MCM0; operation continues on the
Whether the CPU is operating on the internal high-speed oscillation clock or the high-speed system clock can be
Caution When switching the internal high-speed oscillation clock to the high-speed system clock, bit 2
Remarks 1. The number of clocks listed in Table 5-7 is the number of main system clocks before switchover.
The following lists the register flag settings for stopping the clock oscillation (disabling external clock input) and
Switchover
Table 5-6. Time Required for Switchover of CPU Clock and Main System Clock Cycle Division Factor
0
0
1
1
0
0
1
0
1
0
(XSEL) of MCM must be set to 1 in advance. The value of XSEL can be changed only once after a
reset release.
2. Calculate the number of clocks in Table 5-7 by removing the decimal portion.
Set Value Before Switchover
Example When switching the main system clock from the internal high-speed oscillation clock to the
PCC2 PCC1 PCC0 PCC2 PCC1 PCC0 PCC2 PCC1 PCC0 PCC2 PCC1 PCC0 PCC2 PCC1 PCC0
0
Table 5-7. Maximum Time Required for Main System Clock Switchover
8 clocks
4 clocks
2 clocks
1 clock
MCM0
0
0
high-speed system clock (@ oscillation with f
1 + 2f
0
RH
/f
XH
0
= 1 + 2 × 16/12 = 1 + 2 × 1.33 = 1 + 2.66 = 3.66 → 3 clocks
Preliminary User’s Manual U19014EJ1V0UD
CHAPTER 5 CLOCK GENERATOR
16 clocks
4 clocks
2 clocks
1 + 2f
1 clock
0
RH
/f
XH
1
clock
Set Value After Switchover
0
Set Value After Switchover
16 clocks
8 clocks
2 clocks
1 clock
1
MCM0
RH
0
1
= 16 MHz, f
0
16 clocks
8 clocks
4 clocks
1 clock
XH
1
= 12 MHz)
1
1
16 clocks
8 clocks
4 clocks
2 clocks
0
111
0