HD64F3437TF16 Datasheet, PDF (502/752 Pages) Hitachi Semiconductor – 12 V must not be applied to the S-mask model (single-power-supply specification), as this may permanently damage the device.

Formula: When using a clock frequency not shown in tables 20.9 (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 15.8 µs or less and 6.25 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.
a (f) to d (f) = ^{Clock frequency f [MHz]} × 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:
a (f) = ¹² × 19 = 22.8 ≈ 22 = H'0016
10
b (f) = ¹² × 7 = 8.4 ≈ 9 = H'09
10
c (f) = ¹² × 4 = 4.8 ≈ 5 = H'05
10
d (f) = ¹² × 3906 = 4687.2 ≈ 4687 = H'124F
10
Table 20.10 Watchdog Timer Overflow Interval Settings (#e Setting Value According to
Clock Frequency)
Clock Frequency [MHz]
10 MHz ≤ frequency ≤ 16 MHz
2 MHz ≤ frequency < 10 MHz
Variable
e (f)
H'A57F
H'A57E
473