
105
CHAPTER 5 CLOCK GENERATOR
User
’
s Manual U15017EJ2V0UD
(3) Oscillation stabilization time specification register (OSTS)
This register specifies the operation of the oscillator. Either a crystal/ceramic resonator or external clock is set
to the EXTC bit in OSTS as the clock used. The STOP mode can be set even during external clock input only
when the EXTC bit is set 1.
OSTS is set using a 1-bit or 8-bit transfer instruction.
RESET input sets OSTS to 00H.
Figure 5-4. Format of Oscillation Stabilization Specification Register (OSTS)
Address: 0FFCFH After reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
OSTS
EXTC
0
0
0
0
OSTS2
OSTS1
OSTS0
EXTC
External clock selection
0
Crystal/ceramic resonator is used
1
External clock is used
EXTC
OSTS2
OSTS1
OSTS0
Oscillation stabilization time selection
0
0
0
0
2
19
/f
XX
(41.9 ms)
0
0
0
1
2
18
/f
XX
(21.0 ms)
0
0
1
0
2
17
/f
XX
(10.5 ms)
0
0
1
1
2
16
/f
XX
(5.2 ms)
0
1
0
0
2
15
/f
XX
(2.6 ms)
0
1
0
1
2
14
/f
XX
(1.3 ms)
0
1
1
0
13
/f
XX
(655
μ
s)
0
1
1
1
2
12
/f
XX
(328
μ
s)
1
×
×
×
512/f
XX
(41.0
μ
s)
Cautions
1. When a crystal/ceramic resonator is used, make sure to clear the EXTC bit to 0. If the
EXTC bit is set to 1, oscillation stops.
2. When using the STOP mode during external clock input, make sure to set the EXTC bit
to 1 before setting the STOP mode. If the STOP mode is used during external clock input
when the EXTC bit of OSTS has been cleared to 0, the
μ
PD784975A may be damaged or
its reliability may be impaired.
3. If the EXTC bit is set to 1 during external clock input, the opposite phase of the clock input
to the X1 pin must be input to the X2 pin. If the EXTC bit is set to 1, the
μ
PD784975A only
operates with the clock input to the X2 pin.
Remarks 1.
The values in parentheses are valid for operation when f
XX
is 12.5 MHz.
2.
×
: don
’
t care