TNETA1585

ATM TRAFFIC MANAGEMENT SCHEDULER DEVICE

WITH RECEIVE UTOPIA AND COPROCESSOR INTERFACES

SDNS041A – NOVEMBER 1996 – REVISED JULY 1998

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POST OFFICE BOX 655303

RM-cell-contents FIFO D

When the TNETA1575 reads the next-cell register and an indication is given that an RM cell should be sent from

the RM-cell contents FIFO D, the TNETA1575 must make 12 accesses to control-memory location 10004h to

fetch one entire cell payload. The data that is returned by the TNETA1585 is in big-endian format as follows:

Byte 0 (31–24)

Byte 1 (23–16)

Byte 2 (15–8)

Byte 3 (7–0)

The ordering and formatting of data (as it is sequentially read from this register) is:

Word 0 – Bytes 0, 1, 2, 3

Word 1 – Bytes 0, 1, 2, 3

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coprocessor interface

The coprocessor interface consists of a group of unidirectional serial channels through which real-time

information concerning the transmission and reception of cells by the SAR/switch port is passed between the

TNETA1585 and the SAR/switch port. Reset and interrupt capabilities also are provided by the coprocessor

interface. The unidirectional serial-interface implementation by the TNETA1575 SAR is described below.

Similar requirements apply when interfacing to a different SAR device or a switch port. The coprocessor

interface consists of:

Received cell-indication interface (RCCX)

Transmitted cell-indication interface (TCCX)

Data-availability interface (DAX)

COP full-indication interface (COPFULL)

received-cell-indication interface (RCCX)

A serial-bit interface allows the TNETA1575 to signal to the TNETA1585 that a cell has been received on the

UTOPIA interface on a particular channel. This interface is necessary to avoid duplicating the hardware that

is used to resolve a virtual path identifier (VPI) or virtual channel identifier (VCI) to a channel number. When a

cell is received, the VPI/VCI value from the header is extracted by the TNETA1575 and is used as a key in a

lookup algorithm to resolve its associated channel number. When the lookup is complete, the TNETA1575

passes relevant information to the TNETA1585 by sending a 13-bit frame formatted as follows:

Channel number (12–2)

Good/bad cell indicator (1)

Framing (0)

Bits 12–2 (channel number). These bits indicate on which of the 2K channels the last cell was received.

Bit 1 (good/bad cell indicator). This bit indicates whether or not the last cell passed the lookup test or if it should

be discarded. The bit is encoded as follows:

BIT 1

INDICATION

0

Cell is good (VPI/VCI was found in the lookup)

1

Cell should be discarded

Bit 0 (framing). This bit is set to a 1 to denote the start of a frame.

The frame is transmitted to the TNETA1585 through the RCCX terminal starting with bit 0. When a frame is not

actively being transmitted, the RCCX terminal is driven to a 0.