CS8900 View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
CS8900 Datasheet PDF : 132 Pages
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CS8900
6.0 TEST MODES
Loopback & Collision Diagnostic Tests
Internal and external Loopback and Collision
tests can be used to verify the CS8900’s func-
tionality when configured for either 10BASE-T
or AUI operation.
Internal Tests
Internal tests allow the major digital functions to
be tested, independent of the analog functions.
During these tests, the Manchester encoder is
connected to the decoder. All digital circuits are
operational, and the transmitter and receiver are
disabled.
External Tests
External test modes allow the complete chip to
be tested without connecting it directly to an
Ethernet network.
Loopback Tests
During Loopback tests, the internal Carrier Sense
(CRS) signal, used to detect collisions, is ig-
nored, allowing packet reception during packet
transmission.
10BASE-T Loopback and Collision Tests
10BASE-T Loopback and Collision Tests are
controlled by two bits in the Test Control regis-
ter: FDX (Register 19, TestCTL, Bit E) and
ENDECloop (Register 19, TestCTL, Bit 9). Ta-
ble 6.1 describes these tests.
AUI Loopback and Collision Tests
AUI Loopback and Collision tests are controlled
by two bits in the Test Control register: AUIloop
(Register 19, TestCTL, Bit A) and ENDECloop
(Register 19, TestCTL, Bit 9). Table 6.2 de-
scribes these tests.
Test Mode FDXforce
10BASE-T Internal
1
Loopback
10BASE-T
0
Internal
Collision
10BASE-T
1
External Loopback
10BASE-T
0
External
Collision
ENDECloop
1
1
0
0
Description of Test
Transmit a frame and verify that the frame is received without error.
Transmit frames and verify that collisions are detected and that internal
counters function properly. After 16 collisions, verify that 16coll (Register 8,
TxEvent, Bit F) is set.
Connect TXD+ to RXD+ and TXD- to RXD-. Transmit a frame and verify
that the frame is received without error.
Connect TXD+ to RXD+ and TXD- to RXD-. Transmit frames and verify
that collisions are detected and that internal counters function properly.
After 16 collisions, verify that 16coll (Register 8, TxEvent, Bit F) is set.
Table 6.1. 10BASE-T Loopback and Collision Tests
DS150PP2
107
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