Reset And Nmi Input Noise Filters - Epson S1C17001 Technical Manual

7.7 RESET and NMI Input Noise Filters

Since accidental activation of RESET or NMI by noise in the S1C17 core input signal will cause unintended reset-
ting or NMI processing, the OSC module incorporates noise filters operated by the system clock. The filters remove
noise from these signals before they reach the S1C17 core.
Separate noise filters are used for each signal. You can select to use or bypass them individually. All are active im-
mediately after the initial resetting.
RESET input noise filter: Filters noise when RSTFE (D1/OSC_NFEN register) = 1; bypassed when RSTFE = 0
NMI input noise filter:
∗ RSTFE: Reset Noise Filter Enable Bit in the Noise Filter Enable (OSC_NFEN) Register (D1/0x5062)
∗ NMIFE: NMI Noise Filter Enable Bit in the Noise Filter Enable (OSC_NFEN) Register (D0/0x5062)
The noise filters operate using the system clock (OSC3 or OSC1 clock) divided to 1/8. When activated, they filter
out noise with pulses not exceeding two clock cycles.
This means the pulse width must be at least 16 cycles of the system clock to input as a valid signal.
Note: • All noise filters should normally be enabled.
• The S1C17001 does not feature external NMI input pins, but the watchdog timer NMI re-
quest signal passes through these filters.
S1C17001 TECHNICAL MANUAL
Filters noise when NMIFE (D0/OSC_NFEN register) = 1; bypassed when NMIFE = 0
EPSON
7 OSCILLATOR CIRCUIT (OSC)
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