pnx1700 NXP Semiconductors, pnx1700 Datasheet - Page 291

• Manufacturer Part Number: pnx1700
• Description: Connected Media Processor
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Volume 1 of 1
PNX17XX_SER_1
Preliminary data sheet
Figure 11: Examples of Duty Cycles for Ir TX Signals
IROUT
Actual Sub-carrier Freq.
Programmed Freq.
3.2 Spike Filtering
In the 33% and 66% duty-cycle cases FREQ_DIV must be programmed such that the
resulting frequency is 3 times the actual sub-carrier frequency, i.e the minimum pulse
width (high or low) is programmed. Similarly, in the 50% duty-cycle case FREQ_DIV
must be programmed such that the resulting frequency is 2 times the actual sub-
carrier frequency.
33%
When signal sampling at a programmed frequency a filtering feature is available in
the GPIO module which filters out spikes which may occur on a Ir RX signal. This
feature is enabled by programming the EN_IR_FILTER and IR_FILTER registers. The
IR_FILTER value represents the spike filter pulse width, i.e all pulses less than the
IR_FILTER pulse width are considered spikes and not passed through to the signal
monitoring control.
Rev. 1 — 17 March 2006
Actual Sub-carrier Freq.
Programmed Freq.
50%
Chapter 8: General Purpose Input Output Pins
Actual Sub-carrier Freq.
Programmed Freq.
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
66%
PNX17xx Series
8-20