CHAPTER 15 STANDBY FUNCTION
Preliminary User’s Manual U16846EJ1V0UD
296
(2) Oscillation stabilization time select register (OSTS)
This register is used to select the oscillation stabilization wait time of the high-speed system clock when STOP
mode is released. The wait time set by OSTS is valid only after STOP mode is released when the high-speed
system clock is selected as the CPU clock. After STOP mode is released when the Ring-OSC clock is selected,
check the oscillation stabilization time using OSTC.
OSTS can be set by an 8-bit memory manipulation instruction.
RESET input sets OSTS to 05H.
Figure 15-2. Format of Oscillation Stabilization Time Select Register (OSTS)
Address: FFA4H After reset: 05H R/W
Symbol
7 6 5 4 3 2 1 0
OSTS
0 0 0 0 0
OSTS2
OSTS1
OSTS0
Oscillation stabilization time selection
OSTS2 OSTS1 OSTS0
f
XP
= 10 MHz
f
XP
= 16 MHz
0 0 1
2
11
/f
XP
204.8
µ
s 128
µ
s
0 1 0
2
13
/f
XP
819.2
µ
s 512
µ
s
0 1 1
2
14
/f
XP
1.64 ms
1.02 ms
1 0 0
2
15
/f
XP
3.27 ms
2.04 ms
1 0 1
2
16
/f
XP
6.55 ms
4.09 ms
Other than above
Setting prohibited
Cautions 1. If the STOP mode is entered and then released while the Ring-OSC clock is
being used as the CPU clock, set the oscillation stabilization time as follows.
•
Desired OSTC oscillation stabilization time
≤
Oscillation stabilization time
set by OSTS
The oscillation stabilization time counter counts only during the oscillation
stabilization time set by OSTS. Therefore, note that only the statuses during the
oscillation stabilization time set by OSTS are set to OSTC after STOP mode has
been released.
2. The wait time when STOP mode is released does not include the time after
STOP mode release until clock oscillation starts (“a” below) regardless of
whether STOP mode is released by RESET input or interrupt generation.
a
STOP mode release
X1 pin voltage
waveform
Remark f
XP
: High-speed system clock oscillation frequency