background image

TL/F/12034

Loopback

Diagnostics

Using

the

DP8390/901/902/905

AN-937

National Semiconductor
Application Note 937
Bonnie Wilson
July 1994

Loopback Diagnostics
Using the DP8390/
901/902/905

1.0 OVERVIEW

Loopback capabilities are provided on the DP8390/901/
902/905 to perform certain tests in order to validate opera-
tion of the device prior to transmission and reception of
packets on a live network. Typically these tests may be per-
formed during power up and initialization of a node.

This document describes the different loopback modes and
their operation in the DP8390/901/902/905. There are sev-
eral restrictions during loopback that are also discussed.
Detailed instructions on how to generate different loopback
tests are given, as well as the actual code that generates
the tests (Appendix A). This document also discusses varia-
tions in loopback results caused by several common config-
uration errors.

Throughout this document, the term NIC refers to the con-
troller, SNI refers to the ENDEC, CTI refers to the Coaxial
Transceiver Interface, and TPI refers to the Twisted Pair
Interface. These devices comprise the NIC chip set. The
NIC family consists of the DP8390, DP83901, DP83902, and
DP83905.

The loopback diagnostics verify:

1. The integrity of the data path through each block; re-

ceived data is checked against transmitted data.

2. The CRC logic’s capability to generate good CRC on

transmit.

3. The CRC checking capability of the NIC on receive.

4. The address recognition logic’s ability to accept packets

that have a matching address and reject packets that fail
to match an address.

TL/F/12034 – 1

FIGURE 1. Loopback Mode 1: Through the Controller Module

C

1995 National Semiconductor Corporation

RRD-B30M75/Printed in U. S. A.

Содержание DP8390

Страница 1: ...that generates the tests Appendix A This document also discusses varia tions in loopback results caused by several common config uration errors Throughout this document the term NIC refers to the con...

Страница 2: ...TL F 12034 2 FIGURE 2 Loopback Mode 2 Through the Encoder Decoder TL F 12034 3 FIGURE 3 Loopback Mode 3 Through the TPI or CTI 2...

Страница 3: ...isters TBCR0 and TBCR1 are decremented 2 The NIC generates 56 bits of preamble followed by an 8 bit Start of Frame Delimiter 3 Data is transferred from the FIFO to the serializer 4 If the Inhibit CRC...

Страница 4: ...Register to 21h followed by a wait state of at least 1 5 ms for the NIC to reset c Program the desired loopback mode into the Transmit Configuration Register 6 Loopback only operates with byte wide t...

Страница 5: ...er to 21h If the NIC is currently receiving a packet it will wait for the reception of the current packet to complete before it will reset Thus a wait state of at least 1 5 ms is necessary to insure t...

Страница 6: ...tus Register is set The packet received bit is set only if status is written to memory In loopback this action does not occur hence the Packet Received bit remains 0 for all loopback modes Internal Lo...

Страница 7: ...SR ISR Mode 3 CTI 06H 1FH 0CH 02H 08H If the coax cable is disconnected the results will differ from those listed in Section 6 1 as follows Loopback Path TCR RCR TSR RSR ISR Mode 1 NIC 02H 1FH 40H 02H...

Страница 8: ...cription in Section 6 1 When executed the FIFO and register contents are printed to an output file output txt unless specified differently Refer to AN 874 Writing Drivers for the DP8390 NIC Family of...

Страница 9: ...TL F 12034 8 9...

Страница 10: ...TL F 12034 9 10...

Страница 11: ...TL F 12034 10 11...

Страница 12: ...ional Semiconductor National Semiconductor National Semiconductores National Semiconductor Corporation GmbH Japan Ltd Hong Kong Ltd Do Brazil Ltda Australia Pty Ltd 2900 Semiconductor Drive Livry Garg...

Отзывы: