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7 ClOCK GeneRaTOR (ClG)
S1C17153 TeChniCal Manual
Seiko epson Corporation
7-3
(Rev. 1.0)
Stabilization wait time at start of OSC3B oscillation
The OSC3B oscillator circuit includes an oscillation stabilization wait circuit to prevent malfunctions due
to unstable clock operations at the start of OSC3B oscillation—e.g., when the OSC3B oscillator is turned
on with software. Figure 7.3.1.2 shows the relationship between the oscillation start time and the oscillation
stabilization wait time.
Oscillation enable bit
(OSC3BEN/OSC1EN)
Oscillation waveform
Digitized oscillation waveform
Oscillator output clock
(f
OSC3B
/f
OSC1A
)
System supply wait time
Oscillation start time
Oscillation stabilization wait time
3.1.2 Oscillation Start Time and Oscillation Stabilization Wait Time
Figure 7.
The OSC3B clock is not supplied to the system until the time set for this circuit has elapsed.
Use OSC3BWT[1:0]/CLG_WAIT register to select one of four oscillation stabilization wait times.
3.1.2 OSC3B Oscillation Stabilization Wait Time Settings
Table 7.
OSC3BWT[1:0]
Oscillation stabilization wait time
0x3
8 cycles
0x2
16 cycles
0x1
32 cycles
0x0
64 cycles
(Default: 0x0)
This is set to 64 cycles (OSC3B clock) after an initial reset. This means the CPU can start operating when the
CPU operation start time at initial reset indicated below (at a maximum) has elapsed after the reset state is can-
celed. For the oscillation start time, see the “Electrical Characteristics” chapter.
CPU operation start time at initial reset
≤
OSC3B oscillation start time (max.) + OSC3B oscillation stabili-
zation wait time (64 cycles)
When the system clock is switched to OSC3B immediately after turning the OSC3B oscillator on, the OSC3B
clock is supplied to the system after the OSC3B clock system supply wait time indicated below (at a maximum)
has elapsed. If the power supply voltage V
DD
has stabilized sufficiently, OSC3BWT[1:0] can be set to 0x3 to
reduce the oscillation stabilization wait time.
OSC3B clock system supply wait time
≤
OSC3B oscillation start time (max.) + OSC3B oscillation stabi-
lization wait time
OSC1a Oscillator
7.3.2
The OSC1A oscillator is a high-precision, low-speed oscillator circuit that uses a 32.768 kHz crystal resonator.
The OSC1A clock is generally used as the timer operation clock (for the real-time clock, clock timer, watchdog
timer, and 16-bit PWM timer) and an operation clock for the UART, sound generator, and LCD driver. It can be
used as the system clock instead of the OSC3B clock to reduce power consumption when no high-speed processing
is required.
Figure 7.3.2.1 shows the OSC1A oscillator configuration.