NEC 78K0 Series User Manual page 140

Table 6-2. Relationship Between CPU Clock and Minimum Instruction Execution Time
CPU Clock (f )
CPU
f 0.2
XP
f /2 0.4
XP
2
f /2 0.8
XP
3
f /2 1.6
XP
4
f /2 3.2
XP
f /2
SUB
Note The main clock mode register (MCM) is used to set the main system clock supplied to CPU clock (high-
speed system clock/internal high-speed oscillation clock) (see Figure 6-6).
(3) Setting of operation mode for subsystem clock pin
The operation mode for the subsystem clock pin can be set by using bit 6 (XTSTART) of the processor clock
control register (PCC) and bits 5 and 4 (EXCLKS, OSCSELS) of the clock operation mode select register
(OSCCTL) in combination.
Table 6-3. Setting of Operation Mode for Subsystem Clock Pin
PCC OSCCTL
140
CHAPTER 6 CLOCK GENERATOR
Minimum Instruction Execution Time: 2/f
Main System Clock
Note
High-Speed System Clock
At 10 MHz At 20 MHz
Operation Operation
µ µ
s 0.1 s
µ µ
s 0.2 s
µ µ
s 0.4 s
µ µ
s 0.8 s
µ µ
s 1.6 s
−
Preliminary User's Manual U17260EJ3V1UD
Internal High-Speed
Note
Oscillation Clock
At 8 MHz (TYP.) Operation
µ
0.25 s (TYP.)
µ
0.5 s (TYP.)
µ
1.0 s (TYP.)
µ
2.0 s (TYP.)
µ
4.0 s (TYP.)
−
CPU
Subsystem Clock
At 32.768 kHz Operation
−
−
−
−
−
µ
122.1 s