CS8900A
Crystal LAN™ ISA Ethernet Controller
6.0 TEST MODES
6.0.4 Loopback Tests
During Loopback tests, the internal Carrier Sense
(CRS) signal, used to detect collisions, is ignored,
allowing packet reception during packet transmis-
sion.
6.0.1 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 op-
eration.
6.0.5 10BASE-T Loopback and Collision Tests
10BASE-T Loopback and Collision Tests are con-
trolled by two bits in the Test Control register:
FDX (Register 19, TestCTL, Bit E) and ENDE-
Cloop (Register 19, TestCTL, Bit 9). Table 36 de-
scribes these tests.
6.0.2 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.
6.0.6 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 37 describes
these tests.
6.0.3 External Tests
External test modes allow the complete chip to be
tested without connecting it directly to an Ethernet
network.
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
0
1
0
0
Transmit frames and verify that collisions are detected and
that the internal counters function properly. After 16 collli-
sions, verify that 16coll (Register 8, TxEvent, Bit F) is set.
10BASE-T
External Loop-
back
Connect TXD+ to RXD+ and TXD- to RXD-. Transmit a frame
and verify that the frame is received without error.
10BASE-T
External Collision
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 36. 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 37. AUI Loopback and Collision Tests
CIRRUS LOGIC PRODUCT DATA SHEET
106
DS271PP3
CIRRUS [ CIRRUS LOGIC ]
