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9.7.5
Application Notes
1. When reading the values in ECH and ECL, first clear bits CUEH and CUEL to 0 in ECCSR to
prevent asynchronous event input to the counter. The correct value will not be returned if the
event counter increments while being read.
When clear bits CUEH and CUEL to 0 in ECCSR, ECH and ECL sometimes count up.
2. Use a clock with a frequency of up to 16 MHz (Internal step-down circuit not used: V
CC
= 4.5
to 5.5 V), up to 10 MHz (Internal step-down circuit not used: V
CC
= 2.7 to 5.5 V), up to 4
MHz (internal step-down circuit not used: V
CC
= 1.8 to 5.5 V), up to 10 MHz (V
CC
= 2.7 to
5.5 V), up to 4 MHz (V
CC
= 1.8 to 5.5 V) for input to the AEVH and AEVL pins, and ensure
that the high and low widths of the clock are at least 30 ns. The duty cycle is immaterial.
Mode
Maximum AEVH/AEVL Pin
Input Clock Frequency
16-bit mode
Internal step-down circuit
8-bit mode
Active (high-speed), sleep (high-speed)
not used:
V
CC
= 4.5 to 5.5 V/16 MHz
V
CC
= 2.7 to 5.5 V/10 MHz
V
CC
= 1.8 to 5.5 V/4 MHz
Internal step-down circuit
used:
V
CC
= 2.7 to 5.5 V/10 MHz
V
CC
= 1.8 to 5.5 V/4 MHz
8-bit mode
Active (medium-speed), sleep (medium-speed) (ø/16)
(ø/32)
(ø/64)
f
OSC
= 1 MHz to 16 MHz
(ø/128)
2 · f
OSC
f
OSC
1/2 · f
OSC
1/4 · f
OSC
8-bit mode
Watch, subactive, subsleep, standby
(øw/2)
(øw/4)
øw = 32.768 kHz or 38.4 kHz
(øw/8)
1000 kHz
500 kHz
250 kHz
3. When AEC uses with 16-bit mode, set CUEH in ECCSR to “1” first, set CRCH in ECCSR to
“1” second, or set both CUEH and CRCH to “1” at same time before clock entry. While AEC
is operating on 16-bit mode, do not change CUEH. Otherwise, ECH will be miscounted up.