DP83241 CDD Device (FDDI Clock Distribution Device)
February 1991
DP83241 CDD
TM
Device
(FDDI Clock Distribution Device)
General Description
The CDD device is a clock generation and distribution de-
vice intended for use in FDDI (Fiber Distributed Data Inter-
face) networks The device provides the complete set of
clocks required to convert byte wide data to serial format for
fiber medium transmission and to move byte wide data be-
tween the PLAYER
TM
and BMAC
TM
devices in various sta-
tion configurations 12 5 MHz and 125 MHz differential ECL
clocks are generated for the conversion of data to serial
format and 12 5 MHz and 25 MHz TTL clocks are generated
for the byte wide data transfers
Features
Y
Y
Y
Y
Y
Y
Y
Y
Y
Provides 12 5 MHz and 25 MHz TTL clocks
12 5 MHz and 125 MHz ECL clocks
5 phase TTL local byte clocks eliminate clock
skew problems in concentrators
Internal VCO requires no varactors coils or
adjustments
Option for use of High Q external VCO
125 MHz clock generated from a 12 5 MHz crystal
External PLL synchronizing reference for
concentrator configurations
28-pin PLCC package
BiCMOS processing
TL F 10385 鈥?1
FIGURE 1-1 FDDI Chip Set Block Diagram
TRI-STATE is a registered trademark of National Semiconductor Corporation
BMAC
TM
BSI
TM
CDD
TM
CRD
TM
and PLAYER
TM
are trademarks of National Semiconductor Corporation
C
1995 National Semiconductor Corporation
TL F 10385
RRD-B30M105 Printed in U S A