am79c981 Advanced Micro Devices, am79c981 Datasheet - Page 23

• Manufacturer Part Number: am79c981
• Description: Integrated Multiport Repeater Plus? Imr+? ??9
• Manufacturer: Advanced Micro Devices

IMR+ Chip External Components
Figure 6 shows a typical twisted pair port external com-
ponents schematic. The resistors used should have a
1% tolerance to ensure interoperability with 10BASE-T
compliant networks. The filters and pulse transformers
are necessary devices that have a major influence on
the performance and compliance of the 10BASE-T ports
of the repeater. Specifically, the transmitted waveforms
are heavily influenced by the filter characteristics and
Notes:
1. Compatible filter modules, with a brief description of package type and features are included in the Appendix.
2. The resistor values are recommended for general purpose use and should allow compliance to the 10BASE-T specification
Notes:
1. Compatible AUI transformer modules, with a brief description of package type and features are included in the Appendix.
2. The differential input DI and the CI pairs are externally terminated by two 40.2
for template fit and jitter performance. However, the overall performance of the transmitter is also affected by the transmit
filter configuration.
mode bypass capacitor. The differential input impedance, ZIDF, and the common-mode input impedance, ZICM, are speci-
fied so that the Ethernet specification for cable termination impedance is met using standard 1% resistor terminators. If SIP
devices are used, 39
Am79C981
is the nearest usable equivalent value.
Am79C981
Figure 7a. Typical TP Port External Components
RXD+
RXD–
TXD+
TXD–
TXP+
TXP–
Figure 7b. Typical AUI Port Components
Optional
DO+
DO–
DI+
DI–
CI+
CI–
0.1 F
61.9
422
61.9
422
40.2
PRELIMINARY
Am79C981
ANLG GND
40.2
40.2
Note 2
1.21K
100
the twisted pair receivers employ several criteria to con-
tinuously monitor the incoming signal’s amplitude and
timing characteristics to determine when and if to assert
the internal carrier sense. For these reasons, it is crucial
that the values and tolerances of the external compo-
nents 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.
40.2
0.1 F
Transformer
Note 1
Filter
Filter
XMT
RCV
Note 1
Pulse
Transformer
Module
Filter &
1:1
1:1
1% resistors and one optional common-
Connector
17306B-13
AUI
10
12
3
5
2
9
Connector
TD+
TD–
RD+
RD–
RJ45
17306B-12
3
2
6
1
AMD
1–93