5

FN2951.3

October 15, 2008

Repeater Operation

Manchester Il data can be presented to the repeater in either

of two ways. The inputs Bipolar One In and Bipolar Zero In

will accept data from differential inputs such as a comparator

or sensed transformer coupled bus. The input Unipolar Data

In accepts only noninverted Manchester II coded data. The

decoder requires a single clock with a frequency 16X or 32X

the desired data rate. This clock is selected to 16X with

Speed Select low and 32X with Speed Select high. For long

data links the 32X mode should be used as this permits a

wider timing jitter margin.

The inputs UDl, or BOl, BZl are delayed approximately 1/2

bit period and repeated as outputs BOO and BZO. The 2X

ECLK is transmitted out of the repeater synchronously with

BOO and BZO.

A low on CTS enables ECLK, BOO, and BZO. In contrast to

the converter mode, a transition on CTS does not initiate a

synchronization sequence of eight 0’s and a command sync.

The repeater mode does recognize a command or data sync

pulse. SD/CDS is an output which reflects the state of the

most recent sync pulse received, with high indicating a

command sync and low indicating a data sync.

When RST is low, the outputs SDO, DCLK, and NVM are

low, and SRST is set low. SRST remains low after RST goes

high and is not reset until a sync pulse and two valid

manchester bits are received with the reset bit low. The reset

bit is the first data bit after the sync pulse. With RST high,

NRZ Data is transmitted out of Serial Data Out

synchronously with the 1X DCLK.

FIGURE 2. DECODER OPERATION

DCLK

UDI

SDO

RST

NVM

COMMAND

SYNC

10

01

01

0

1

0

1

0

1

0

FIGURE 3. REPEATER OPERATION

INPUT

COUNT

ECLK

UDI

BZO

BOO

RST

SRST

SYNC PULSE

12

3

45

6

7

HD-6409

HD-6409