TNETA1500

155.52-MBIT/S SONET/SDH ATM RECEIVER/TRANSMITTER

SDNS021D – MARCH 1994 – REVISED JANUARY 1998

5

POST OFFICE BOX 655303

transmit operation (continued)

Table 1. Transmit Transport-Overhead and Path-Overhead Bytes

SONET FRAME

SDH FRAME

OVERHEAD BYTE

VALUE WHEN

SDHENABLE = LOW

VALUE WHEN

SDHENABLE = HIGH

A1

1111 0110 (F6h)

1111 0110 (F6h)

A2

0010 1000 (28h)

0010 1000 (28h)

C1 bytes

01 02 03 (h)

01 00 00 (h)

B1

B2

Calculated

Calculated

B3

First H1

0110 0010 (62h)

0110 1010 (6Ah)

Second H1 (H1*)

1001 0011 (93h)

1001 1011 (9Bh)

Third H1 (H1*)

1001 0011 (93h)

1001 1011 (9Bh)

First H2

0000 1010 (0Ah)

0000 1010 (0Ah)

Second H2 (H2*)

1111 1111 (FFh)

1111 1111 (FFh)

Third H2 (H2*)

1111 1111 (FFh)

1111 1111 (FFh)

Three H3 bytes

0000 0000 (00h)

0000 0000 (00h)

First K2

Normal operation: 0000 0000

Line FERF: 0000 0110

Normal operation: 0000 0000

Line FERF: 0000 0110

Third Z2

B2 error count:

0000 0000–0001 1000

B2 error count:

0000 0000–0001 1000

J1

0000 0000

0000 0000

C2

0001 0011

0001 0011

G1

Bits 1–4

B3 error count: 0000–1000

Path FERF: 1001

B3 error count: 0000–1000

Path FERF: 1001

G1

Bit 5

Path RDI: 1

Path RDI: 1

Bits 6–8

000

000

H4

0000 0000

0000 0000

The parity byte B1, B2 (three bytes), and B3 are calculated as follows:

B1 – B1 is a bit-interleaved parity-8 code (BIP-8) using even parity. B1 is calculated over all bits of the

previous STS-3c frame after scrambling. The calculated value of B1 is placed in the STS-3c frame before

the frame is scrambled.

B2 – For an STS-3c frame, the three B2 bytes combine to form a BIP-24 code; however, each B2 byte is

calculated as if the frame is composed of three individual STS-1s. Each B2 is calculated over all bits of the

line overhead and STS-1 envelope capacity of the previous STS-1 frame before scrambling, using even

parity. The computed value is placed in the appropriate B2 byte location before scrambling. The line

overhead consists of the six rows of transport-overhead bytes, beginning with the first H1 byte and ending

before the row containing the first A1 byte (see Table 1).

B3 – For an STS-3c frame, the B3 byte is calculated over all bits of the previous STS-3c SPE before

scrambling. B3 is a BIP-8 code using even parity. The computed value is placed in the B3 location before

scrambling.