dp83840a National Semiconductor Corporation, dp83840a Datasheet - Page 33

• Manufacturer Part Number: dp83840a
• Description: 10/100 Mb/s Ethernet Physical Layer
• Manufacturer: National Semiconductor Corporation

Version A
3.0 Functional Description
3.7.15 Typical Node Application
An example of the 10BASE-T interface is shown in Figure
17. The TXS+/- signals are used for STP and the TXU+/-
signals for UTP. Standard UTP applications do not require
connection of the TXS+/- outputs. The output resistor
values are chosen to match the transmit output impedance
to the impedance of the twisted pair cable.
The DP83840A 10BASE-T outputs require a 1:2 step-up
isolation transformer in order to match the cable
impedance. The 10BASE-T inputs require a 1:1 isolation
transformer and appropriate line termination. Refer to
Figure 16.
DP83840A
TXU+
LED1
LED2
LED3
LED4
LED5
TXS+
TXU-
TXS-
RXI+
RXI-
Note: Resistors from TXS + / - outputs can
be added if STP cable support is required.
49.9
1%
10.5
10.5
16.5
16.5
FIGURE 17. Typical 10BASE-T Node Application
(Continued)
1%
1%
1%
1%
0.01 F
1.5K
1.5K
1.5K
1.5K
1.5K
49.9
1%
5%
5%
5%
5%
5%
(For STP applications, the RXI+/- termination
resistors should each be 75 +/-1%)
33
3.8 IEEE 1149.1 CONTROLLER
The IEEE 1149.1 standard defines a test access port and
boundary-scan architecture for digital integrated circuits
and for the digital portions of mixed analog/digital
integrated circuits. Figure 18 depicts the IEEE 1149.1
architecture.
The standard provides a solution for testing assembled
printed circuit boards and other products based on highly
complex digital integrated circuits and high-density surface-
mounting assembly techniques. It also provides a means of
accessing and controlling design-for-test features built into
the digital integrated circuits. Such features include internal
scan paths and self-test functions as well as other features
intended to support service applications in the assembled
0.01 F
0.01 F
National Semiconductor
1:2
1:1
V
CC
LOW CURRENT LEDS
INTERFACE
10BASE-T
TD+
TD-
RD+
RD-
RJ45