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CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Oscillation Circuit)
4.3.6 I/O memory of oscillation circuit
Table 4.3.6.1 shows the I/O address and the control bits for the oscillation circuit.
Register
Address
D3
D2
0
0
CLKCHG OSCC
0F6H
R
∗1
Initial value at initial reset
∗2
Not set in the circuit
OSCC: OSC3 oscillation control register (0F6H•D0)
Controls oscillation for the OSC3 oscillation circuit.
When "1" is written: OSC3 oscillation ON
When "0" is written: OSC3 oscillation OFF
Reading: Valid
When it is necessary to operate the CPU at high speed or output a remote control carrier signal, set OSCC
to "1". At other times, set it to "0" to reduce current consumption.
At initial reset, this register is set to "1".
CLKCHG: CPU system clock switching register (0F6H•D1)
The CPU's operation clock is selected with this register.
When "1" is written: OSC1 clock is selected
When "0" is written: OSC3 clock is selected
Reading: Valid
When the CPU clock is to be OSC3, set CLKCHG to "0"; for OSC1, set CLKCHG to "1".
After turning the OSC3 oscillation ON (OSCC = "1"), switching of the clock should be done after waiting
5 msec or more.
At initial reset, this register is set to "0".
4.3.7 Programming notes
(1) It takes at least 5 msec from the time the OSC3 oscillation circuit goes on until the oscillation stabi-
lizes. Consequently, when switching the CPU operation clock from OSC1 to OSC3, do this after a
minimum of 5 msec have elapsed since the OSC3 oscillation went on.
Further, the oscillation stabilization time varies depending on the external oscillator characteristics
and conditions of use, so allow ample margin when setting the wait time.
(2) When switching the clock from OSC3 to OSC1, use a separate instruction for switching the OSC3
oscillation off. An error in the CPU operation can result if this processing is performed at the same
time by the one instruction.
14
Table 4.3.6.1 Control bits of oscillation circuit
∗1
D1
D0
Name Init
∗3
∗2
0
–
∗3
∗2
0
–
CLKCHG
0
R/W
OSCC
1
∗3
Always "0" being read
∗4
Reset (0) immediately after being read
1
0
–
–
Unused
–
–
Unused
OSC1
OSC3
CPU clock change
On
Off
OSC3 oscillation on/off
EPSON
Comment
∗5 Undefined
E0C6006 TECHNICAL MANUAL
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