XRT91L31 datasheet(9/41 Pages) EXAR

9 / 41 page

XRT91L31

REV. 1.0.2

STS-12/STM-4 OR STS-3/STM-1 SONET/SDH TRANSCEIVER

TRANSMITTER SECTION

NAME

LEVEL

TYPE

DESCRIPTION

TXDI0

TXDI1

TXDI2

TXDI3

TXDI4

TXDI5

TXDI6

TXDI7

LVTTL,

LVCMOS

Transmit Parallel Data Input

Transmit Parallel Clock Output Operation

The 77.76 Mbps (STS-12/STM-4) / 19.44 Mbps (STS-3/STM-1)

8-bit parallel transmit data should be applied to the transmit

parallel bus and simultaneously referenced to the rising edge of

the TXPCLK_IO clock output. The 8-bit parallel interface is mul-

tiplexed into the transmit serial output interface with the MSB

first (TXDI[7:0]).

Alternate Transmit Parallel Clock Input Operation

When operating is this mode, TXPCLK_IO is no longer a paral-

lel clock output reference but reverses direction and serves as

the parallel transmit clock input reference for the PISO (Parallel

Input to Serial Output) block. The 77.76 Mbps (STS-12/STM-4)

/ 19.44 Mbps (STS-3/STM-1) 8-bit parallel transmit data should

be applied to the transmit parallel bus and simultaneously refer-

enced to the rising edge of the TXPCLK_IO clock input.

TXOP

TXON

LVPECL Diff

Transmit Serial Data Output

The transmit serial data stream is generated by multiplexing the

8-bit parallel transmit data input into a 622.08 Mbps STS-12/

STM-4 or 155.52 Mbps STS-3/STM-1 serial data stream.

TXPCLK_IO

LVTTL,

LVCMOS

I/O

Transmit Parallel Clock Input/Output (77.76/19.44 MHz)

Transmit Parallel Clock Output Operation

When the PIO_CTRL pin 48 is asserted "High," this pin will out-

put a 77.76 MHz (STS-12/STM-4) or 19.44 MHz (STS-3/STM-

1) clock output reference for the 8-bit parallel transmit data

input TXDI[7:0]. This clock is used by the framer/mapper device

to present the TXDI[7:0] data which the XRT91L31 will latch on

the rising edge of this clock. This enables the framer/mapper

device and the XRT91L31 transceiver to be in synchronization.

Alternate Transmit Parallel Clock Input Operation

When the PIO_CTRL pin 48 is asserted "Low," this pin will

accept a 77.76 MHz (STS-12/STM-4) or 19.44 MHz (STS-3/

STM-1) clock input reference for the 8-bit parallel transmit data

input TXDI[7:0]. The XRT91L31 will latch data at TXDI[7:0] on

the rising edge of this clock. This has the enormous advantage

of enabling the framer/mapper device transmit timing to be syn-

chronized with the transceiver transmit timing.

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