PM7341 datasheet(71/413 Pages) PMC

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PRELIMINARY

INVERSE MULTIPLEXING OVER ATM

PM7341 S/UNI-IMA-84

DATASHEET

PMC-2000223

ISSUE 4

INVERSE MULTIPLEXING OVER ATM

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

Conceptually, the Any-PHY protocol can be divided into two processes: polling

and cell transfer.

Polling in the transmit direction is used by the bus master – typically a traffic

buffering and management device – to determine when a buffered data cell can

be safely sent to a PHY. The S/UNI-IMA-84 provides an independent 3-deep cell

buffer FIFO for each virtual PHY. In total, there are 84 FIFOs. This arrangement

ensures that there is no head-of-line blocking, while providing latitude to the

master for servicing high data rate ports as well as low data rate ports.

The traffic manager need only poll those virtual PHYs for which it has cells

queued. A cell transfer can be initiated after a polled virtual PHY asserts the TPA

output. Each virtual PHY’s cell buffer availability status (i.e., the status that will be

driven onto the TPA output when the virtual PHY is polled) is deasserted when

the first byte of the last cell is written into the buffer. It is re-asserted only when

the FIFO can accept another complete cell.

In Any-PHY mode, polling is performed using the TADR[10:0] bus in conjunction

with the TCSB. Each S/UNI-IMA-84 uses the TADR[6:0] bits to indicate the 84

logical virtual PHYs. The upper bits from the TADR bus, TADR[10:7], are

compared to the configured address to select the device. The remaining address

bits from the traffic manager are decoded externally and are used to drive the

TCSB. The address prepend field in the cell transfer contains the entire 16-bit

address. In 8-bit mode, the prepend address is reduced to 8-bits.

In Any-PHY mode, the cell transfer is initiated after a successful poll. The virtual

PHY address is prepended to the cell, thus performing an inband selection. The

S/UNI-IMA-84 monitors the address prepend on the cell transfer to detect its

cells.

10.1.1.3

Transmit Cell Transfer Format

The Transmit Cell Transfer Format is shown in Figure 5 and Figure 6. Word/byte

0 is required for cell transfers to an Any-PHY slave. The address prepend is the

S/UNI-IMA-84 virtual PHY ID. The virtual PHY ID can be mapped to a TC link or

to an IMA group. Optional prepends are supported, but are ignored by the S/UNI-

IMA-84.

Inclusion of optional words is statically configurable for the interface. The optional

words are always ignored.

PM7341 Datasheet(PDF) 71 Page - PMC-Sierra, Inc

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