AN983B Datasheet, PDF (66/91 Pages) List of Unclassifed Manufacturers – PCI/miniPCI-to-Ethernet LAN Controller

AN983B PCI/miPCI Fast Ethernet Controller with integrated PHY
1. IFG1 time (64-bit time): If a carrier is detected on the medium during this time, the
AN983B will reset the IFG1 time counter and restart to monitor the channel for an idle again.
2. IFG2 time (32-bit time): After counting the IFG2 time the AN983B will access the channel
even though a carrier has been sensed on the network.
Collision Handling
The scheduling of re-transmissions is determined by a controlled randomization process
called “truncated binary exponential back-off”. At the end of enforcing a collision (jamming),
the AN983B delays before attempting to re-transmit the packet. The delay is an integer
multiple of slot time. The number of slot times to delay before the nth re-transmission
attempt is chosen as a uniform distributed integer r in the range:
0 r 2^k where k = min(n, 10)
8.5.2 TRANSCEIVER OPERATION
In the transceiver portion of the AN983B, it integrates the IEEE802.3u compliant functions of PCS
(physical coding sub-layer), PMA (physical medium attachment) sub-layer, and PMD (physical
medium dependent) sub-layer for 100BASE-TX, and the IEEE802.3 compliant functions of
Manchester encoding/decoding and transceiver for 10BASE-T. All the functions and operation
schemes are described in the following sections.
100BASE-TX Transmit Operation
Regarding the 100BASE-TX transmission, the transceiver provides the transmission
functions of PCS, PMA, and PMD for encoding of MII data nibbles to five-bit code-groups
(4B/5B), scrambling, serialization of scrambled code-groups, converting the serial NRZ code
into NRZI code, converting the NRZI code into MLT3 code, and then driving the MLT3 code
into the category 5 Unshielded Twisted Pair cable through an isolation transformer with the
turns ratio of 1: 1.
Data code-groups Encoder:
In normal MII mode application, the transceiver receives nibble type 4B data via the
TxD0~3 inputs of the MII. These inputs are sampled by the transceiver on the rising
edge of Tx-clk and passed to the 4B/5B encoder to generate the 5B code-group used by
100BASE-TX.
Idle code-groups
In order to establish and maintain the clock synchronization, the transceiver needs to
keep transmitting signals to medium. The transceiver will generate Idle code-groups
for transmission when there is no real data want to be sent by MAC.
Rev. 1.8
ADMtek Inc.
www.admtek.com.tw