Epson S1C63666 Technical Manual page 37

Switching to high-speed operation
The S1C63666 is designed with twin clock specifications; it has two types of oscillation circuits OSC1
(for low-speed operation) and OSC3 (for high-speed operation) built-in. Use OSC1 clock for normal
operation, and switch it to OSC3 using software when high-speed operation is necessary. When
switching the clock, the operating voltage V
operation of the oscillation circuit and internal circuits.
The following shows the switching procedure. Refer to Section 4.4, "Oscillation Circuit", for control of
the oscillation circuit.
Switching from low-speed operation to high-speed operation
1. Set VDC2 to "0". (low-speed operation voltage regulator: halver mode → normal mode)
2. Set VDC1 to "1". (high-speed operation voltage regulator: off → on)
3. Set VDC0 to "1". (internal logic operating voltage: V
4. Wait 2.5 msec or more.
5. Set OSCC to "1". (OSC3 oscillation: off → on)
6. Wait 5 msec or more.
7. Set CLKCHG to "1". (CPU clock: OSC1 → OSC3)
To switch from high-speed operation to low-speed operation, follow the procedure to set the halver
mode (see the previous page).
4.2.3 I/O memory for power control
Table 4.2.3.1 shows the I/O address and the control bits for power control.
Register
Address
D3 D2
VDC3 VDC2 VDC1
FF00H
R/W
LDUTY1 LDUTY0 STCD
FF60H
R/W
*1 Initial value at initial reset
*2 Not set in the circuit
*3 Constantly "0" when being read
VDC0: Internal logic system power switching register (FF00H•D0)
It is used to switch the operating voltage for the CPU and internal circuit.
When "1" is written: V
When "0" is written: V
Reading: Valid
When "1" is written to VDC0, the internal operating voltage is switched to V
the OSC3 oscillation can be started.
When the low-speed operation voltage regulator is in the halver mode, return it to the normal mode
before switching to V
D3
When "0" is written to VDC0, the internal operating voltage is switched to V
before switching to V
D1L
At initial reset, this register is set to "0".
S1C63666 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Power Control)
Table 4.2.3.1 Power control bits
∗1
D1 D0 Name Init
VDC3 0
VDC0
VDC2 0
VDC1 0
VDC0 0
LDUTY1 0
LPWR
LDUTY0 0
STCD 0
LPWR 0
(for OSC3 operation)
D3
(for OSC1 operation)
D1L
.
.
must be switched using software to stabilize the
D1
→ V
)
D1L D3
1 0
1/2V V
LCD system voltage regulator power source switch
DD DD
1/2V V Low-speed operation voltage regulator power source switch
DD DD
On Off High-speed operation voltage regulator on/off
V V
Logic system power source switch
D3 D1L
LCD drive duty
switch
LCD drive switch
Static Dynamic
LCD power On/Off
On Off
EPSON
Comment
[LDUTY1, 0] 0 1
Duty 1/4 1/5
. After switching to V
D3
. Stop the OSC3 oscillation
D1L
2, 3
1/8
,
D3
27