DP83907VF National Semiconductor, DP83907VF Datasheet - Page 20

• Manufacturer Part Number: DP83907VF
• Description: IC CONTROLLR AT/LANII TP 160PQFP
• Manufacturer: National Semiconductor

Specifications of DP83907VF

• Controller Type: Network Interface Controller (NIC)
• Interface: Twisted Pair
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 150mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 160-MQFP, 160-PQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *DP83907VF

4 0 Functional Description
4 10 ENCODER DECODER (ENDEC) MODULE
The ENDEC consists of four main logical blocks
a) The oscillator generates the 10 MHz transmit clock sig-
b) The Manchester encoder accepts NRZ data from the
c) The Manchester decoder receives Manchester data from
d) The collision translator indicates to the controller the
Oscillator
The oscillator is controlled by a 20 MHz parallel resonant
crystal connected between X1 and X2 or by an external
clock on X1 The 20 MHz output of the oscillator is divided
by 2 to generate the 10 MHz transmit clock for the control-
ler The oscillator also provides internal clock signals to the
encoding and decoding circuits
CRYSTAL OPERATION
If the crystal used with the internal oscillator circuit is not
properly selected the DP83907 oscillator may not reliably
start oscillation under all conditions
If this occurs it could be deceiving to a designer since his
prototypes may work fine However when the designer
does qualification testing or starts production he may en-
nal for system timing
controller encodes the data to Manchester and trans-
mits the data differentially to the transceiver through the
differential transmit driver
the transceiver converts it to NRZ data and clock puls-
es and sends it to the controller
presence of a valid 10 MHz collision signal to the PLL
FIGURE 18 Encoder Decode Block Diagram
(Continued)
20
counter a higher than expected board yield loss due to the
oscillator not starting The DP83907’s oscillator circuit
clocks the Encoder-Decoder logic The DP83907’s oscilla-
tor also clocks the twisted pair interface block If the oscilla-
tor does not start the DP83907 will not be able to transmit
or receive
FIGURE 19 Crystal Connection to DP83907
(see text for component values)
TL F 12082 – 13
TL F 12082 – 14