tdat04622 ETC-unknow, tdat04622 Datasheet - Page 82

• Manufacturer Part Number: tdat04622
• Description: Tdat Sonet/sdh 155/622/2488 Mbits/s Data Interfaces
• Manufacturer: ETC-unknow

TDAT042G5 SONET/SDH
155/622/2488 Mbits/s Data Interface
Functional Description
Overhead Processor (OHP) Block
The TOAC inserter must insert the first bit of A1 at the TOAC input, TxTOHD[D:A], during the first clock cycle when
TxTOHF = 1. The TOAC has a built-in parity checker. For the parity check, the value of the first inserted bit of A1
must be set to the parity value of the previous frame. The remainder of the inserted bits of the A1, A2 bytes are
ignored by the transmit framer.
Receive OHP
Loss-of-Signal. The loss-of-signal block monitors the incoming scrambled data for the absence of transitions.
When an absence of transitions is detected for a programmable length of time, a loss-of-signal (LOS) is declared.
LOS is cleared when two valid framing patterns are detected, and during the intervening time, no LOS condition is
detected.
Framer. The frame block finds and locks onto the incoming A1 and A2 bytes of the SONET transport overhead.
Loss-of-frame (LOF) is declared when a defect persists for more than 3 ms. LOF is cleared when the defect is
absent for more than 3 ms. To prevent intermittent out-of-frame/in-frame conditions, the 3 ms timer is not reset to
zero until an in-frame (or out-of-frame) condition persists for 3 ms. The framer is also responsible for performing bit
rotations on the incoming data stream to ensure that the rest of the IC receives byte-aligned data.
While in-frame, the A1/A2 framing bytes in each frame are compared against the expected pattern. Out-of-frame
(OOF) is declared when five consecutive frames containing one or more framing pattern errors have been
received.
While out-of-frame, this block will monitor the receive data stream for an occurrence of the framing pattern. When a
framing pattern has been recognized, the framer performs the necessary bit rotation and verifies that an error-free
framing pattern is present in the next frame before declaring in-frame.
J0 Section Trace. The section trace message is extracted and stored in a 16-byte memory for access by software.
The first byte of the message can be provisioned to be either:
I
I
J0 mismatch detection is provided using one of four methods (provisionable via J0MONMODE[A—D][1:0]; see reg-
ister description, page 173).
Descrambler. The descrambler block implements the frame synchronous SONET descrambler with a generating
polynomial of 1 + x
not descrambled. The descrambler may be disabled through a software register.
54
The byte with the most significant bit (MSB) set high (for SDH), or
The byte following a carriage return (0x0D) and line feed (0x0A) sequence (for SONET).
6
+ x
7
. The framing bytes (A1, A2), the section trace bytes (J0), and the growth bytes (Z0) are
(continued)
(continued)
Agere Systems Inc.
Data Sheet
May 2001