PM7344 datasheet(50/293 Pages) PMC

50 / 293 page

PM7344 S/UNI-MPH

DATA SHEET

PMC-950449

ISSUE 6

MULTI-PHY USER NETWORK INTERFACE

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

Pin Name

Type

No.

Function

TCAMPH

I/O

Transmit Multi-Phy Cell Available (TCAMPH).

The TCAMPH signal is output on this pin when

input MPHEN is high. This signal indicates

when a cell is available in the transmit FIFO for

the port selected by TWA[1:0]. When high,

TCAMPH indicates that the corresponding

transmit FIFO is not full and a complete cell may

be written. When TCAMPH goes low, it can be

configured to indicate either that the

corresponding transmit FIFO is near full and can

accept no more than four writes or that the

corresponding transmit FIFO is full. TCAMPH

will thus transition low on the rising edge of

TFCLK on which the 52nd or 48th byte is

sampled if the PHY being polled is the same as

the PHY in use. To reduce FIFO latency, the

FIFO depth at which TCAMPH indicates "full"

can be set to one, two, three or four cells.

TWRENB[4

]

Transmit Write Enable PHY #4 (TWRENB[4]).

The TWRENB[4] signal is input on this pin when

input MPHEN is low. TWRENB[4] is used to

initiate writes to the transmit FIFO of PHY #4.

When sampled low using the rising edge of

TFCLK (and the remaining three TWRENBs

remain high), a byte is written to PHY #4's

synchronous FIFO. When sampled high using

the rising edge of TFCLK, no write is performed.

TWRENB[4] must operate in conjunction with

TFCLK to access the FIFOs at a high enough

instantaneous rate as to avoid FIFO overflows.

The ATM layer device may deassert

TWRENB[4] at anytime it is unable to provide

another byte.

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