NEC UPD98413 User Manual page 77

(1) Transmitting the APS (Automatic Protection Switching) code
The APS function is provided to switch a signal into an auxiliary signal in case a line fails. The switching
operation is requested, confirmed, or acknowledged by using the K1 and K2 bytes in OH in a line-multiplexed
zone and by using the commands and protocols defined by ANSI T1.105.01 or ITU-T G.783. Transmission
method is as follows:
• • • • Transmitting/Terminating method
Set the APS signal to be transferred to the K12T register of the OH insert register. The µ PD98413 loads the
contents of the K12T register to the positions of the K1 and K2 bytes and transmits them each time it has
transmitted a frame. To change or clear the contents of the APS signal, change the contents of the K12T
register. The contents of the K1 and K2 bytes can also be input from the OH insert interface.
Bits 6 to 8 of the K2 byte are also used to transmit alarm Line RDI or Line AIS. If the transmission of alarm
Line RDI or Line AIS is specified, the setting of K2T[2:0], the portion of the K12T register equivalent to these
bits, is ignored and alarm transmission takes precedence.
Bits 6 to 8 of the K2 byte are also ignored even when they are input from the OH insert interface.
(2) Transmitting Line AIS (Line Alarm Indication Signal)
Line AIS is a line alarm indication signal that detects a failure in the upstream and sends an alarm to the
downstream during relaying.
• • • • Transmitting / Terminating method
The Line AIS frame can be transmitted in the following two ways. The frame is transmitted or terminated by
observing the boundary of the frame.
<1> Set the LAIS bit of the CMALM register to 1. While this bit is set to 1, the Line AIS frame is transmitted.
<2> Drive the TALM pins to the Line AIS code. While these pins are set to the Line AIS code, the Line AIS
frame is transmitted. See section 4.7
• • • • Line AIS frame
This frame has "1" in all the bits of all the areas (LOH + POH + SPE) of a transmit frame, except the SOH area.
(3) Transmitting Path AIS (Path Alarm Indication Signal)
Path AIS is a Path Alarm Indication Signal that is reported to the downstream when a failure is detected in the
upstream and alarm is issued during relaying.
• • • • Transmitting/Terminating method
The Path AIS frame can be transmitted in the following two ways. The frame is transmitted or cleared by
observing the boundary of the frame.
<1> Set the PAIS bit of the CMALM register to 1. While this bit is set to 1, the Path AIS frame is transmitted.
<2> Drive the TALM pins to the Path AIS code. While these pins are set to the Path AIS code, the Path AIS
frame is transmitted.
• • • • Path AIS frame
This frame has "1" in all the H1, H2, and H3 bytes of the AU pointer of the OH byte of a transmit frame, and all
the bits in the SPE area (POH and payload) before frame scramble.
CHAPTER 3 FUNCTIONAL OUTLINE
PRELIMINARY
NEC confidential and Proprietary
77