Cs8900a – Cirrus Logic CS8900A User Manual
Page 68
68
DS271F5
CS8900A
Crystal LAN™ Ethernet Controller
CIRRUS LOGIC PRODUCT DATASHEET
Disable Backoff
When set, the backoff algorithm is disabled. The CS8900A transmitter looks only for completion
of the inter packet gap before starting transmission. When clear, the backoff algorithm is used.
FDX
When set, 10BASE-T full duplex mode is enabled and CRS (Register 14, LineST, Bit E) is ig-
nored. This bit must be set when performing loopback tests on the 10BASE-T port. When clear,
the CS8900A is configured for standard half-duplex 10BASE-T operation.
At reset, if no EEPROM is found by the CS8900A, then the register has the following initial state. If an EEPROM is
found, then the register’s initial value may be set by the EEPROM. See Section 3.3 on page 19.
Reset value is: 0000 0000 0001 1001
4.4.23 Register 1C: AUI Time Domain Reflectometer
(Read-only, Address: PacketPage base + 013Ch)
The TDR counter (Bits 6 through F) is a time domain reflectometer useful in locating cable faults in 10BASE-2 and
10BASE-5 coax networks. It counts at a 10 MHz rate from the beginning of transmission on the AUI to when a col-
lision or Loss-of-Carrier error occurs. The TDR counter is cleared when read.
011100
These bits provide an internal address used by the CS8900A to identify this as the Bus Status
Register. When reading this register, these bits will be 011100, where the LSB corresponds to
Bit 0.
AUI-Delay
The upper ten bits contains the number of 10 MHz clock periods between the beginning of
transmission on the AUI to when a collision or Loss-of-Carrier error occurs.
Reset value is: 0000 0000 0001 1100
7
6
5
4
3
2
1
0
AUI Delay
011100
F
E
D
C
B
A
9
8
AUI Delay