dp83241 National Semiconductor Corporation, dp83241 Datasheet - Page 12

• Manufacturer Part Number: dp83241
• Description: Cdd Device Fddi Clock Distribution Device
• Manufacturer: National Semiconductor Corporation

5 0 Detailed Information
5 2 CONCENTRATOR AND DUAL ATTACH STATION
CONFIGURATIONS
5 2 1 Concentrator Applications
An application where many of the features of the CDD de-
vice are used is a FDDI concentrator A concentrator is
used to connect several workstations and peripherals to a
single node in the network A concentrator provides the abil-
ity to easily bypass or insert multiple stations into the net-
work The CDD device in each station is driven from a com-
mon oscillator instead of each CDD device being driven by
its own crystal In a small concentrator the same LBC
phase can be used in each station since the data flight time
from one board to another is small compared to the LBC
Crystal Resonator
Varactor Diode
VHF NPN Transistor
Inductor
FIGURE 5-3 Small Concentrator Application
(Continued)
TABLE 5-1 Special External Components
Part
Manufacturer
Key Specifications
Part
Manufacturer
Key Specifications
Part
Manufacturer
Key Specifications
Part
Manufacturer
Key Specifications
12
period and the skew between the CDD devices on the two
boards is minimal In a larger concentrator configuration
where this skew becomes too large the data setup time of
the downstream station will be directly impacted One way
to avoid this problem is to latch data into the next station
The strobe for the latch will be supplied by one of the LBC
outputs from the upstream station’s CDD device An LBC
output phase is chosen that occurs after the physical layer
data is stable Assuming that the data and LBC flight times
are equal the LBC output will latch data for the next station
The LBC output phase should be selected to give the opti-
mum setup and hold time for the receiving station’s physical
layer function
C5410N
NEL
12 5000 MHz Center Frequency
20 PPM Accuracy 0 C to
15 pF Load Capacitance
MV2105
Motorola
Cap Tolerance
PN3563
National Semiconductor
1
Turns
g
10%
TL F 10385 – 8
a
70 C