Formula: When using a clock frequency not shown in tables 19.9 (1) and (2), follow the formula
below. The calculation is based on a clock frequency of 10 MHz.
After calculating a(f) and d(f) in the decimal system, omit the first decimal figures, and convert
them to the hexadecimal system, so that a(f) and d(f) are set to 20 µs or less and 10 ms or less,
respectively.
After calculating b(f) and c(f) in the decimal system, raise the first decimal figures, and convert
them to the hexadecimal system, so that b(f) and c(f) are set to 4 µs or more and 2 µs or more,
respectively.
Clock frequency f [MHz]
a (f) to d (f) =
× a (f = 10) to d (f = 10)
10
Examples for a program running in on-chip memory (RAM) at a clock frequency of 12 MHz:
12
a (f) =
b (f) =
c (f) =
d (f) =
×
×
×
25
7
=
=
=
30
8.4
4.8
≈
≈
≈
30 = H'001E
10
12
10
9
5
= H'09
= H'05
12
10
4
12
10
× 6250 = 7500 ≈ 7500 = H'1D4C
Table 19.10 Watchdog Timer Overflow Interval Settings (#e Setting Value According to
Clock Frequency)
Variable
Clock Frequency [MHz]
e (f)
10 MHz ≤ frequency ≤ 16 MHz
2 MHz ≤ frequency < 10 MHz
H'A57F
H'A57E
411
HITACHI [ HITACHI SEMICONDUCTOR ]
