
I-54
EPSON
S1C88348/317/316/308 TECHNICAL HARDWARE
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Oscillation Circuits and Operating Mode)
CLKCHG: 00FF02HD3
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).
5.4.7 Control of oscillation circuit and operating mode
Table 5.4.7.1 shows the control bits for the oscillation circuits and operating modes.
Table 5.4.7.1 Oscillation circuit and operating mode control bits
VDC1, VDC0: 00FF02HD1, D0
Selects the operating mode according to supply
voltage and operating frequency.
Table 5.4.7.2 shows the correspondence between
register preset values and operating modes.
Table 5.4.7.2 Correspondence between register
preset values and operating modes
OSCC: 00FF02HD2
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).
2.4–5.5 V
1.8–3.5 V
3.5–5.5 V
Operating
frequency
4.2 MHz
50 kHz
8.2 MHz
VD1
2.2 V
1.3 V
3.3 V
VDC1
0
1
VDC0
0
1
×
Normal mode
Low power mode
High speed mode
(Max.)
Operating
mode
Power
voltage
*
The VD1 voltage is the value where VSS has been
made the standard (GND).
At initial reset, this register is set to "0" (normal
mode).
Address Bit
Name
SR R/W
Function
Comment
10
00FF02
D7
D6
D5
D4
D3
D2
D1
D0
EBR
WT2
WT1
WT0
CLKCHG
OSCC
VDC1
VDC0
Bus release enable register
(K11 and R51 terminal specification)
Wait control register
CPU operating clock switch
OSC3 oscillation On/Off control
Operating mode selection
*1
*1 This is just R/W register on S1C88308.
0
R/W
BREQ
BACK
OSC3
On
WT2
1
0
WT1
1
0
1
0
Number
of state
14
12
10
8
6
4
2
No wait
Input port
Output port
OSC1
Off
K11
R51
VDC1
1
0
VDC0
×
1
0
High speed (VD1=3.3V)
Low power (VD1=1.3V)
Normal
(VD1=2.2V)
WT0
1
0
1
0
1
0
1
0
Operating mode