AM79C98 Advanced Micro Devices, AM79C98 Datasheet - Page 10

• Manufacturer Part Number: AM79C98
• Description: Twisted-Pair Ethernet Transceiver (TPEX)
• Manufacturer: Advanced Micro Devices

10
In both modes, the jabber circuitry, collision detection,
and collision oscillator functions are disabled and the
AUI and RXD+/– squelch circuits are active.
TPEX External Components
Figure 1 shows a typical twisted-pair port external
components schematic. The resistors used should
have a 1% tolerance to ensure interoperability with
10BASE-T-compliant networks. Filters and pulse trans-
formers are necessary devices that have a major influ-
ence on the performance and compliance of a TPEX-
Note:
The filter/transformer module shown is available from the following manufacturers: Belfuse, TDK, Pulse Engineering, PCA, Valor
Electronics, and Nano Pulse.
Am79C100
TPEX
TXD+
TXD–
RXD+
RXD–
Figure 1. Typical Twisted-Pair Port External Components
TXP+
TXP–
57.6
324.0
57.6
324.0
100
768.0
Am79C98
RECV
XMIT
Filter
Filter
based MAU. Specifically, the transmitted waveforms
are heavily influenced by filter characteristics and the
twisted-pair receivers employ several criteria to contin-
uously monitor the incoming signal’s amplitude and
timing characteristics to determine when and if to as-
sert the internal carrier sense. For these reasons, it is
crucial that the values and tolerances of the external
components be as specified. Several manufacturers
produce a module that combines the functions of the
transmit and receive filters and the pulse transformers
into one package.
Module
1:1
1:1
RD+
RD–
TD+
TD–
Twisted-Pair
Cable
14395D-5