PM7347 datasheet(269/341 Pages) PMC

269 / 341 page

S/UNI®-JET Data Sheet

Released

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use

269

Document ID: PMC-1990267, Issue 3

13.5

G.751 E3 Frame Format

The S/UNI-JET provides support for the G.751 E3 frame format, shown in Figure 13. This format

can be extended to allow for direct byte mapping or PLCP mapping of ATM cells.

Figure 13 G.751 E3 Frame Structure

RAI Na

C11 C21 C31 C41

C12 C22 C32 C42

C13 C23 C33 C43 J1 J2

J3 J4

372 Payload bits

380 Payload bits

376 Payload bits

The processing of the overhead bits in the G.751 E3 frame is described in Table 39. In the

transmit direction, the overhead bits can be inserted on a bit-by-bit basis from a user supplied data

stream using the TOH, TOHINS, TOHFP, and TOHCLK signals. In the receive direction, most of

the overhead bits are brought out serially on the ROH data stream.

When used to transport ATM cells in either ATM direct mapping mode or with PLCP framing,

bits 13, 14, 15, and 16 of the E3 frame (directly following the RAI and Na bits) are set to 1, 1, 0

and 0.

Table 39 G.751 E3 Frame Overhead Operation

Control Bit

Transmit Operation

Receive Operation

Frame Alignment

Signal

Inserts the frame alignment

signal 1111010000b.

Finds frame alignment by searching for the

frame alignment signal. When the pattern has

been detected for three consecutive frames,

an in-frame condition is declared. When errors

are detected in four consecutive frames, an

OOF condition is declared.

RAI:

RAI

Optionally asserts the RAI

signal under a register

control or when LOS, OOF,

AIS and LCD conditions are

detected.

Extracts the RAI signal and outputs it on the

ROH output pin. The state of the RAI signal is

also written to a register bit.

Na:

National Use Bit

Asserts the National Use bit

under a register control or

from the internal HDLC

controller.

Extracts the National Use bit and stores the

value in a register bit.

Cjk:

Justification Service

Bits

When the device is

configured as an E3 G.751

framer device, the

Justification Service Bits can

be inserted on the TDATI

input pin the same way as

normal payload data.

When the device is

configured for ATM

application, the Justification

Service Bits are used as

payload bits.

Extracts the Justification Service Bits on the

ROH output pin when the Cjk bits are

configured as overhead.

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