NEC 78K0 Series User Manual page 509

(1) Oscillation stabilization time counter status register (OSTC)
This is the register that indicates the count status of the X1 clock oscillation stabilization time counter. When X1
clock oscillation starts with the internal high-speed oscillation clock or subsystem clock used as the CPU clock,
the X1 clock oscillation stabilization time can be checked.
OSTC can be read by a 1-bit or 8-bit memory manipulation instruction.
When reset is released (reset by RESET input, POC, LVI, and WDT), the STOP instruction and MSTOP (bit 7 of
MOC register) = 1 clear OSTC to 00H.
Figure 21-1. Format of Oscillation Stabilization Time Counter Status Register (OSTC)
Address: FFA3H After reset: 00H
Symbol 7
OSTC 0
MOST11
1
1
1
1
1
Cautions 1. After the above time has elapsed, the bits are set to 1 in order from MOST11 and
Remark f
CHAPTER 21 STANDBY FUNCTION
R
6 5
0 0
MOST13 MOST14
0 0
1 0
1 1
1 1
1 1
remain 1.
2. The oscillation stabilization time counter counts up to the oscillation
stabilization time set by OSTS. If the STOP mode is entered and then released
while the internal high-speed oscillation 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
Note, therefore, that only the status up to the oscillation stabilization time set by
OSTS is set to OSTC after STOP mode is released.
3. The X1 clock oscillation stabilization wait time does not include the time until
clock oscillation starts ("a" below).
STOP mode release
X1 pin voltage
waveform
: X1 clock oscillation frequency
X
Preliminary User's Manual U17260EJ3V1UD
4 3
MOST11 MOST13 MOST14
MOST15 MOST16 Oscillation stabilization time status
11
0 0 2 /f
X
13
0 0 2 /f
X
14
0 0 2 /f
X
15
1 0 2 /f
X
16
1 1 2 /f
X
a
2 1 0
MOST15 MOST16
f = 10 MHz f = 20 MHz
X X
µ µ
min. 204.8 s min. 102.4 s min.
µ µ
min. 819.2 s min. 409.6 s min.
µ
min. 1.64 ms min. 819.2 s min.
min. 3.27 ms min. 1.64 ms min.
min. 6.55 ms min. 3.27 ms min.
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