HD64F3437TF16 Datasheet, PDF (213/752 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.

Contention between FRC Write and Increment: If an FRC increment pulse is generated during
the T₃ state of a write cycle to the lower byte of the free-running counter, the write takes priority
and FRC is not incremented.
Figure 8.17 shows this type of contention.
Write cycle:
CPU write to lower byte of FRC
T₁
T₂
T₃
ø
Internal address bus
FRC address
Internal write signal
FRC clock pulse
FRC
N
M
Write data
Figure 8.17 FRC Write-Increment Contention
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