HDMP-1637A datasheet(4/16 Pages) HP

4 / 16 page

FRAME DEMUX AND BYTE

SYNC

The FRAME DEMUX AND BYTE

SYNC block is responsible for

restoring the 10-bit parallel data

from the high speed serial bit

stream. This block is also

responsible for recognizing the

comma character (or a K28.5

character) of positive disparity

(0011111xxx). When

recognized, the FRAME DEMUX

AND BYTE SYNC block works

with the RX PLL/CLOCK

RECOVERY block to properly

align the receive byte clocks to

the parallel data. When a comma

character is detected and

realignment of the receiver byte

clocks (RBC1/RBC0) is

necessary, these clocks are

stretched, not slivered, to the

next possible correct alignment

position. These clocks will be

fully aligned by the start of the

second 2-byte ordered set. The

second comma character

received shall be aligned with the

rising edge of RBC1. As per the

8B/10B encoding scheme,

comma characters must not be

transmitted in consecutive bytes

to allow the receiver byte clocks

to maintain their proper

recovered frequencies.

OUTPUT DRIVERS

The OUTPUT DRIVERS present

the 10-bit parallel recovered data

byte properly aligned to the

receive byte clocks (RBC1/

RBC0), as shown in Figure 5.

These output data buffers

provide TTL compatible signals.

SIGNAL DETECT

The SIGNAL DETECT block

examines the differential

amplitude of the inputs

± DIN.

When this input signal is too

small, it outputs a logic 0 at

SIG_DET (refer to SIG_DET pin

definition for detection

thresholds), and at the same

time, forces the parallel output

RX[0]..RX[9] to all logic one

(1111111111). The main

purpose of this circuit is to

prevent the generation of random

data when the serial input lines

are disconnected. When the

signal at

± DIN is of a valid

amplitude, SIG_DET is set to

logic 1, and the output of the

INPUT SELECT block is passed

through.

HDMP-1637A Datenblatt(PDF) 4 Page - Agilent(Hewlett-Packard)

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