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Section 25 Clock Pulse Generator
25.2
Duty Correction Circuit
The duty correction circuit generates the system clock (φ) by correcting the duty of the clock
output from the oscillator.
25.3
Subclock Input Circuit
The subclock input circuit controls subclock input from the EXCL or ExEXCL pin. To use the
subclock, a 32.768-kHz external clock should be input from the EXCL or ExEXCL pin.
Figure 25.7 shows the relationship of subclock input from the EXCL pin and the ExEXCL pin.
When using a pin to input the subclock, specify input for the pin by clearing the DDR bit of the
pin to 0. The EXCL pin is specified as an input pin by clearing the EXCLS bit in PTCNT0 to 0.
The ExEXCL pin is specified as an input pin by setting the EXCLS bit in PTCNT0 to 1. The
subclock input is enabled by setting the EXCLE bit in LPWRCR to 1.
Figure 25.7 Subclock Input from EXCL Pin and ExEXCL Pin
Subclock input conditions are shown in table 25.5. When the subclock is not used, subclock input
should not be enabled.
Table 25.5 Subclock Input Conditions
Item
Subclock input pulse width
low level
Subclock input pulse width
high level
Subclock input rising time
Subclock input falling time
Rev. 1.00 Apr. 28, 2008 Page 838 of 994
REJ09B0452-0100
EXCLS
(PTCNT0)
P96/EXCL
PE0/ExEXCL
Symbol
Min.
t
EXCLL
t
EXCLH
t
EXCLr
t
EXCLf
EXCLE
(LPWRCR)
Subclock
VCC = 3.0 to 3.6 V
Typ.
Max.
15.26
15.26
10
10
Unit
Test Conditions
µs
Figure 25.8
µs
ns
ns
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