CHAPTER 5 CLOCK GENERATOR
Preliminary User’s Manual U16315EJ1V0UD
107
The fastest instruction can be executed in 2 clocks of the CPU clock in the 78K0/KD1 Series. Therefore, the
relationship between the CPU clock (f
CPU
) and minimum instruction execution time is as shown in the Table 5-2.
Table 5-2. Relationship Between CPU Clock and Minimum Instruction Execution Time
Minimum Instruction Execution Time: 2/f
CPU
CPU Clock (f
CPU
)
X1 Input Clock
Note
(at 10 MHz Operation)
Ring-OSC Clock
Note
(at 240 kHz (TYP.) Operation)
Subsystem Clock
(at 32.768 kHz Operation)
f
X
0.2
µ
s
8.3
µ
s (TYP.)
−
f
X
/2
0.4
µ
s
16.6
µ
s (TYP.)
−
f
X
/2
2
0.8
µ
s
33.2
µ
s (TYP.)
−
f
X
/2
3
1.6
µ
s
66.4
µ
s (TYP.)
−
f
X
/2
4
3.2
µ
s
132.8
µ
s (TYP.)
−
f
XT
/2
−
−
122.1
µ
s
Note
The main clock mode register (MCM) is used to set the CPU clock (X1 input clock/Ring-OSC clock) (see
Figure 5-5
).
(2) Ring-OSC mode register (RCM)
This register sets the operation mode of Ring-OSC.
This register is valid when “Can be stopped by software” is set for Ring-OSC by a mask option, and the X1 input
clock or subsystem clock is selected as the CPU clock. If “Cannot be stopped” is selected for Ring-OSC by a
mask option, settings for this register are invalid.
RCM can be set by a 1-bit or 8-bit memory manipulation instruction.
RESET input clears this register to 00H.
Figure 5-4. Format of Ring-OSC Mode Register (RCM)
Address: FFA0H After reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
RCM
0
0
0
0
0
0
0
RSTOP
RSTOP
Ring-OSC oscillating/stopped
0
Ring-OSC oscillating
1
Ring-OSC stopped
Caution
Make sure that the bit 1 (MCS) of the main clock mode register (MCM) is 1 before
setting RSTOP.
Содержание 78K0/KD1 Series
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