Operation Of Noise Cancellation Function - Fujitsu 8FX Hardware Manual

8-bit microcontroller new 8fx family
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CHAPTER 21 MULTI-PULSE GENERATOR
21.5 Operations
21.5.6

Operation of Noise Cancellation Function

This section describes the noise cancellation function for the SNIx and DTTI
pins.
■ Operation of Noise Cancellation Function
● DTTI Pin Noise Cancellation Function
When the NRSL bit in the 16-bit MPG output control register (upper) (OPCUR) is set to "1",
the noise cancellation function for DTTI pin input can be used. When the noise cancellation
function is selected, the time for fixing an output pin at the inactive level is delayed for about 4,
8, 16 or 32 machine clocks by the noise cancellation circuit.
Note:
Since the DTTI input control circuit uses a peripheral clock, input is invalidated even if the
DTTI input is enabled in a mode such as stop mode in which the oscillator stops.
● SNI2 to SNI0 Pins Noise Cancellation Function
When SNC[2:0] bits in the 16-bit MPG input control register (lower) (IPCLR) are set to "1",
the noise cancellation function for SNI2 to SNI0 pins input can be used. When the noise
cancellation function is selected, the input is delayed for about four machine clocks by the
noise cancellation circuit. Since the noise cancellation circuit uses a peripheral clock, input is
invalidated in a mode such as STOP mode in which the oscillator stops even if the SNIx input
is enabled.
● Programmable Noise Cancellation Circuit
Noise to be cancelled is programmable to have pulse width less than 4, 8, 16 and 32 machine
cycles, i.e. for 16 MHz machine clock, the circuit can filter 0.25 µs to 2 µs width pulses. The
control for the programming of the noise cancellation circuit of the SNIx and DTTI pins are
separated. Section "21.6.9 16-bit MPG Noise Cancellation Control Register (NCCR)" shows
the noise cancellation control register.
420
FUJITSU SEMICONDUCTOR LIMITED
MB95630H Series
MN702-00009-2v0-E

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