N681622YG Nuvoton Technology Corporation of America, N681622YG Datasheet - Page 45

• Manufacturer Part Number: N681622YG
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of N681622YG

• Lead Free Status / RoHS Status: Supplier Unconfirmed

N681386/87
Single Programmable Extended Codec/SLCC
12.1.3.4.
RING TRIP DETECTION
The Ring Trip Detection mechanism is used to recognize an off-hook event during Ringing. The N681386/87
monitors the Loop current through the Loop current circuitry (available at LPI:ILP[11:0] address (0x90)). If the
shadow Linefeed state LS:SLS[7:4] address (0x44)indicates a Ringing state the loop current can used to evaluate
whether a Ring Trip event has occurred under two alternative methods - AC path or DC path.
Figure 14: RING Trip Detection Mechanism
For the AC path the AC component of the loop current is determined by passing it first through a full-wave rectifier to
remove the DC component and then through a Low Pass Filter for smoothing. The resulting value is compared to the
AC path Ring Trip Threshold in register RTTA:ARTT[5:0] address (0x55).
A subsequent debounce filter is
programmed with an AC Path debounce interval from register RTDBA:ARTDI[7:0] address (0x48). If this interval is
satisfied, a valid Ring Trip is judged to have occurred. However, RTLC:RTDUA[3] address (0x46) bit records the
unfiltered status of the AC path Ring Trip Detect without regard to the debounce interval.
For the DC path the DC component of the loop current is determined by passing it first through a Low Pass Filter to
remove the AC component and then though a rectifier to ensure a positive value. The resulting value then compared
against the DC path Ring Trip Threshold in register RTTD:DRTT[5:0] address (0x67) and tested against the DC path
debounce interval from register RTDBD:DRTDI[7:0] address (0x68). If this interval is satisfied, a valid Ring Trip is
judged to have occurred. However, RTLC:RTDUD[4] address (0x46) bit records the unfiltered status of the DC path
Ring Trip Detect without regard to the debounce interval.
If a RingTrip is judged to have occurred either on the AC path or on the DC path RTLC:RTD[1] address (0x46) bit is
set. If enabled, a Ring Trip Interrupt will occur. If LAMC:RGA[1] address (0x43) is set the channel will automatically
transition into the Active state (Forward or Reverse) upon a valid Ring Trip Detect.
Preliminary Datasheet Rev1.0
Page 45 of 164
January 2010