Registers Used During Standby - NEC 78K0S/KB1+ User Manual

14.1.2 Registers used during standby

The oscillation stabilization time after the standby mode is released is controlled by the oscillation stabilization time
select register (OSTS).
Remark For the registers that start, stop, or select the clock, see CHAPTER 5 CLOCK GENERATORS.
(1) Oscillation stabilization time select register (OSTS)
This register is used to select oscillation stabilization time of the clock supplied from the oscillator when the
STOP mode is released. The wait time set by OSTS is valid only when the crystal/ceramic oscillation clock is
selected as the system clock and after the STOP mode is released. If the high-speed internal oscillation or
external clock input is selected as the system clock source, no wait time elapses.
The system clock oscillator and the oscillation stabilization time that elapses after power application or release
of reset are selected by the option byte. For details, refer to CHAPTER 18 OPTION BYTE.
OSTS is set by using the 8-bit memory manipulation instruction.
Figure 14-1. Format of Oscillation Stabilization Time Select Register (OSTS)
Address: FFF4H After reset: Undefined R/W
Symbol 7
OSTS 0
OSTS1 OSTS0
0
0
1
1
Cautions 1. To set and then release the STOP mode, set the oscillation stabilization time as follows.
Expected oscillation stabilization time of resonator ≤ Oscillation stabilization time set
by OSTS
2. The wait time after the STOP mode is released does not include the time from the
release of the STOP mode to the start of clock oscillation ("a" in the figure below),
regardless of whether STOP mode was released by reset signal generation or interrupt
generation.
3. The oscillation stabilization time that elapses on power application or after release of
reset is selected by the option byte. For details, refer to CHAPTER 18 OPTION BYTE.
Remarks 1. ( ): f
X
2. Determine the oscillation stabilization time of the resonator by checking the characteristics of
the resonator to be used.
CHAPTER 14 STANDBY FUNCTION
6 5
0 0
μ
10
0 2 /f (102.4 s)
X
μ
12
1 2 /f (409.6 s)
X
15
0 2 /f (3.27 ms)
X
17
1 2 /f (13.1 ms)
X
STOP mode is released
Voltage
waveform
of X1 pin
= 10 MHz
User's Manual U17446EJ3V1UD
4 3
0 0
Selection of oscillation stabilization time
a
2 1
0 OSTS1 OSTS0
0
237