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EPSON
E0C88832/88862 TECHNICAL MANUAL
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Oscillation Circuits and Operating Mode)
When switching over from the OSC3 to the OSC1,
turn the OSC3 oscillation circuit OFF immediately
following the clock changeover.
The basic clock switching procedure is as described
above, however, you must also combine it with the
changeover of the operating mode to permit low
current consumption and high speed operation.
Figure 5.3.6.1 indicates the status transition dia-
gram for the operation mode and clock changeover.
Note: When turning ON the OSC3 oscillation circuit
after switching the operating mode, you should
allow a minimum waiting time of 5 msec.
5.3.6 Switching the CPU clocks
You can use either OSC1 or OSC3 as the system
clock for the CPU and you can switch over by
means of software.
You can save power by turning the OSC3 oscilla-
tion circuit off while the CPU is operating in OSC1.
When you must operate on OSC3, you can change
to high speed operation by turning the OSC3
oscillation circuit ON and switching over the
system clock. In this case, since several 100
µ
sec to
several 10 msec are necessary for the oscillation to
stabilize after turning the OSC3 oscillation circuit
ON, you should switch over the clock after
stabilization time has elapsed. (The oscillation start
time will vary somewhat depending on the oscilla-
tor and on the externally attached parts. Refer to
the oscillation start time example indicated in
Chapter 7, "ELECTRICAL CHARACTERISTICS".)
*
The return destination from the standby status becomes the program execution status prior to shifting to the standby
status
Fig. 5.3.6.1 Status transition diagram for the operation mode and clock changeover
ON
ON or OFF
STOP
HALT status
OSC1
OSC3
CPU clock
OFF
OFF
STOP
SLEEP status
OSC1
OSC3
CPU clock
Program Execution Status
Standby Status
HALT instruction
SLP instruction
*
Interrupt
*
Interrupt
(Input interrupt)
VDC0=0
VDC1=0
OSCC=0
RESET
OSCC=1
CLKCHG=0
CLKCHG=1
OSCC=0
OSCC=1
CLKCHG=0
CLKCHG=1
ON
OFF
OSC1
ON
OFF
OSC1
ON
ON
OSC1
ON
ON
OSC1
ON
ON
OSC3
ON
ON
OSC3
High speed mode
ON
OFF
OSC1
Normal mode
Low power mode
High speed mode
Normal mode
High speed mode
Normal mode
VDC0=
VDC1=1
VDC0=1
VDC1=0
VDC0=0
VDC1=0
×
OSC1
OSC3
CPU clock
OSC1
OSC3
CPU clock
OSC1
OSC3
CPU clock
OSC1
OSC3
CPU clock
OSC1
OSC3
CPU clock
OSC1
OSC3
CPU clock
OSC1
OSC3
CPU clock
Содержание 0C88832
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