PM7375-SC datasheet(36/430 Pages) PMC

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PM7375 LASAR-155

DATA SHEET

PMC-931127

ISSUE 6

LOCAL ATM SAR & PHYSICAL LAYER

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

TXPHYBP

I/O

The transmit physical layer bypass (TXPHYBP) signal

selects whether or not to bypass the internal SONET

PHY in the transmit direction. When TXPHYBP is set

high, the internal SONET PHY is bypassed and a SCI-

PHY/Utopia compliant interface comprising of signals:

TSOC, TWRENB, TFIFOFB and TDAT[7:0] is

supported. When TXPHYBP is set low, the

LASAR-155 operates normally with the internal

SONET PHY. In this mode, signals TSOC, TWRENB,

TFIFOEB and TDAT[7:0] can be used to interface to

an external FIFO to support CBR VCs.

Under analog test mode as selected using the

PMCATST bit in the LASAR-155 Master Test register,

this pin is configured as an output and is used for test

purposes.

TWRENB

Output

The active low transmit write enable (TWRENB)

signal's function is configured using input TXPHYBP.

When TXPHYBP is set high, the LASAR-155's

SONET physical layer blocks are bypassed and

TWRENB is used to initiate writes to an external FIFO

associated with a physical layer device (e.g. the PMC

SUNI-PDH). When TWRENB is low and TFIFOFB is

high during a SYSCLK cycle, the current cell byte on

bus TDAT[7:0] is written into the external FIFO. When

TWRENB is high during a SYSCLK cycle, no write is

performed. In this mode of operation, TWRENB is

generated using the rising edge of SYSCLK.

When TXPHYBP is set low, the LASAR-155 operates

normally with the integrated STS-3c (STM-1) or STS-1

PHY. When TWRENB is low on the rising edge of a

SYSCLK cycle and TFIFOEB is high, a cell byte is

expected on the TDAT[7:0] bus on the next rising edge

of SYSCLK. When TWRENB is set high on the rising

edge of a SYSCLK cycle, data is not expected on the

TDAT[7:0] bus on the next rising edge of SYSCLK.

Once a full cell is sampled, it is automatically inserted

into the cell stream. In this mode of operation,

TWRENB is generated using the rising edge of

SYSCLK.

PM7375-SC Datasheet(PDF) 36 Page - PMC-Sierra, Inc

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