E0C88832/88862 TECHNICAL MANUAL
EPSON
31
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Oscillation Circuits and Operating Mode)
5.3.7 Control of oscillation circuit and operating mode
Table 5.3.7.1 shows the control bits for the oscillation circuits and operating modes.
Table 5.3.7.1 Oscillation circuit and operating mode control bits
VDC1, VDC0: 00FF02H•D1, D0
Selects the operating mode according to supply
voltage and operating frequency.
Table 5.3.7.2 shows the correspondence between
register preset values and operating modes.
Table 5.3.7.2 Correspondence between register
preset values and operating modes
CLKCHG: 00FF02H•D3
Selects the operating clock for the CPU.
When "1" is written: OSC3 clock
When "0" is written: OSC1 clock
Reading:
Valid
When the operating clock for the CPU is switched
to OSC3, CLKCHG should be set to "1" and when
the clock is switched to OSC1, CLKCHG should be
set to "0".
At initial reset, CLKCHG is set to "0" (OSC1 clock).
2.4–5.5 V
1.8–3.5 V
3.5–5.5 V
Operating
frequency
4.2 MHz
80 kHz
8.2 MHz
V
D1
2.2 V
1.3 V
3.3 V
VDC1
0
0
1
VDC0
0
1
×
Normal mode
Low power mode
High speed mode
(Max.)
(Max.)
(Max.)
Operating
mode
Power
voltage
*
The V
D1
voltage is the value where V
SS
has been
made the standard (GND).
At initial reset, this register is set to "0" (normal
mode).
OSCC: 00FF02H•D2
Controls the ON and OFF settings of the OSC3
oscillation circuit.
When "1" is written: OSC3 oscillation ON
When "0" is written: OSC3 oscillation OFF
Reading:
Valid
When the CPU and some peripheral circuits
(output port, serial interface and programmable
timer) are to be operated at high speed, OSCC is to
be set to "1". At all other times, it should be set to
"0" in order to reduce current consumption.
At initial reset, OSCC is set to "0" (OSC3 oscillation
OFF).
Address Bit
Name
SR R/W
Function
Comment
1
0
00FF02 D7
D6
D5
D4
D3
D2
D1
D0
EBR
WT2
WT1
WT0
CLKCHG
OSCC
VDC1
VDC0
General-purpose register
General-purpose register
General-purpose register
General-purpose register
CPU operating clock switch
OSC3 oscillation On/Off control
Operating mode selection
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
OSC3
On
0
OSC1
Off
VDC1
1
0
0
VDC0
×
1
0
High speed (V
D1
=3.3V)
Low power (V
D1
=1.3V)
Normal (V
D1
=2.2V)
Operating mode
Reserved register
Summary of Contents for 0C88832
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