UPD78F0890GK(A)-GAJ-AX NEC, UPD78F0890GK(A)-GAJ-AX Datasheet - Page 159

• Manufacturer Part Number: UPD78F0890GK(A)-GAJ-AX
• Description: 8BIT MCU, 128K FLASH, 7K RAM, LQFP
• Manufacturer: NEC

Specifications of UPD78F0890GK(A)-GAJ-AX

• Controller Family/series: UPD78F
• No. Of I/o's: 55
• Ram Memory Size: 7KB
• Cpu Speed: 20MHz
• No. Of Timers: 10
• No. Of Pwm: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 128KB
• Oscillator Type: External, Internal

6.6.8 Time required for switchover of CPU clock and main system clock
can be switched (between the main system clock and the subsystem clock) and the division ratio of the main system
clock can be changed.
pre-switchover clock for several clocks (see Table 6-6).
(CLS) of the PCC register.
the internal high-speed oscillation clock and the high-speed system clock).
pre-switchover clock for several clocks (see Table 6-7).
ascertained using bit 1 (MCS) of MCM.
CSS PCC2 PCC1 PCC0
Set Value Before
0
1
By setting bits 0 to 2 (PCC0 to PCC2) and bit 4 (CSS) of the processor clock control register (PCC), the CPU clock
The actual switchover operation is not performed immediately after rewriting to PCC; operation continues on the
Whether the CPU is operating on the main system clock or the subsystem clock can be ascertained using bit 5
By setting bit 0 (MCM0) of the main clock mode register (MCM), the main system clock can be switched (between
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
Switchover
Caution Selection of the main system clock cycle division factor (PCC0 to PCC2) and switchover from
Remarks 1. The number of clocks listed in Table 6-6 is the number of CPU clocks before switchover.
Table 6-6. Time Required for Switchover of CPU Clock and Main System Clock Cycle Division Factor
0
0
0
0
1
×
0
0
1
1
0
×
0
1
0
1
0
×
the main system clock to the subsystem clock (changing CSS from 0 to 1) should not be set
simultaneously.
Simultaneous setting is possible, however, for selection of the main system clock cycle
division factor (PCC0 to PCC2) and switchover from the subsystem clock to the main system
clock (changing CSS from 1 to 0).
2. When switching the CPU clock from the main system clock to the subsystem clock, calculate the
Example When switching CPU clock from f
CSS PCC2 PCC1 PCC0 CSS PCC2 PCC1 PCC0 CSS PCC2 PCC1 PCC0 CSS PCC2 PCC1 PCC0 CSS PCC2 PCC1 PCC0 CSS PCC2 PCC1 PCC0
0
number of clocks by rounding up to the next clock and discarding the decimal portion, as shown
below.
8 clocks
4 clocks
2 clocks
2 clocks
1 clock
0
0
32.768 kHz)
f
XP
0
/f
SUB
0
16 clocks
= 10000/32.768 ≅ 305.1 → 306 clocks
4 clocks
2 clocks
2 clocks
1 clock
0
CHAPTER 6 CLOCK GENERATOR
0
User’s Manual U17554EJ4V0UD
1
0
16 clocks
2 clocks
Set Value After Switchover
8 clocks
2 clocks
1 clock
0
1
XP
/2 to f
0
0
SUB
16 clocks
8 clocks
4 clocks
2 clocks
1 clock
0
/2 (@ oscillation with f
1
1
0
16 clocks
8 clocks
4 clocks
2 clocks
2 clocks
1
0
XP
0
= 10 MHz, f
1
2f
f
f
f
f
XP
XP
XP
XP
XP
/2f
/4f
/8f
/f
/f
×
SUB
SUB
SUB
SUB
SUB
clocks
clocks
clocks
clocks
clocks
×
SUB
159
×
=