Cirrus Logic CS8900A - Manual (Page 107)

DS271F5 107
CS8900A
Crystal LAN™ Ethernet Controller
CIRRUS LOGIC PRODUCT DATASHEET
6.0 TEST
6.1 TEST MODES
6.1.1 Loopback & Collision Diagnostic
Tests
Internal and external Loopback and Collision
tests can be used to verify the CS8900A's
functionality when configured for either
10BASE-T or AUI operation.
6.1.2 Internal Tests
Internal tests allow the major digital functions
to be tested, independent of the analog func-
tions. During these tests, the Manchester en-
coder is connected to the decoder. All digital
circuits are operational, and the transmitter
and receiver are disabled.
6.1.3 External Tests
External test modes allow the complete chip to
be tested without connecting it directly to an
Ethernet network.
6.1.4 Loopback Tests
During Loopback tests, the internal Carrier
Sense (CRS) signal, used to detect collisions,
is ignored, allowing packet reception during
packet transmission.
6.1.5 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 EN-
DECloop (Register 19, TestCTL, Bit 9). Table
37 describes these tests.
6.1.6 AUI Loopback and Collision Tests
AUI Loopback and Collision tests are con-
trolled by two bits in the Test Control register:
AUIloop (Register 19, TestCTL, Bit A) and EN-
DECloop (Register 19, TestCTL, Bit 9). Table
38 describes these tests.
Test Mode FDX ENDECloop Description of Test
10BASE-T Inter-
nal Loopback
1 1 Transmit a frame and verify that the frame is received without
error.
10BASE-T Inter-
nal Collision
0 1 Transmit frames and verify that collisions are detected and
that the internal counters function properly. After 16 collisions,
verify that 16coll (Register 8, TxEvent, Bit F) is set.
10BASE-T
External Loop-
back
1 0 Connect TXD+ to RXD+ and TXD- to RXD-. Transmit a frame
and verify that the frame is received without error.
10BASE-T
External Collision
0 0 Connect TXD+ to RXD+ and TXD- to RXD-. Transmit frames
and verify that collisions are detected and that internal coun-
ters function properly. After 16 collisions, verify that 16coll
(Register 8, TxEvent, Bit F) is set.
Table 37. 10BASE-T Loopback and Collision Tests
Test Mode AUIloop ENDECloop Description of Test
AUI Internal
Loopback
1 1 Transmit a frame and verify that the frame is received without error.
AUI External
Loopback
1 0 Connect DO+ to DI+ and DO- to DI-. Transmit a frame and verify that
the frame is received without error (since there is no collision signal,
an SQE error will occur).
AUI Collision 0 0 Start transmission and observe DO+/DO- activity. Input a 10 MHz
sine wave to Cl+/Cl- pins and observe collisions.
Table 38. AUI Loopback and Collision Tests