MB86967 Datasheet, PDF (32/129 Pages) Fujitsu Component Limited. – LAN Controller with PC Card, ISA Bus, and General-purpose Bus Interfaces

MB86967
The hash filter is used only when the Address Filter mode select bit AF1 is 1 and mode select bit AF0 is 0,
selecting the Node ID, Broadcast, Multicast + Hash Table mode. Hash Table registers should only be accessed
when the Receiver is disabled, i.e., when ENA DLC is high, to avoid interaction with the Receiver. There are
eight bytes of registers in the Hash Table containing 64 one-bit elements, as shown in the Table 7.
9.4 Receive Packet Processing
As a packet arrives from the network, its destination address field is tested for the various address filter criteria
selected by the Address Filter Mode bits, DLCR5<1:0>, and the Hash Table. Only if the address meets the filter
criteria selected will the packet be accepted for storage in the receive buffer. In addition, the packet must be
error-free, unless the chip has been enabled to receive flawed packets for diagnostic purposes. If these conditions
are met, the packet reception results in the packet being stored in the buffer, its 4-byte header being updated
at the end of reception, the BUF EMPTY status bit, DLCR5<6>, being cleared, the RX PKT status bit, DLCR1<7>,
being set high and an interrupt being generated if so enabled. The last four bytes of the packet are the CRC
field and are checked for correct CRC. The CRC bytes are not transferred to the Receive Buffer. If the packet
has an error and reception of such packets has not been enabled, it will be discarded and pointers will be reset
to reuse the same portion of the receive buffer for the next packet to arrive. If a flawed packet is accepted for
storage for diagnostic purposes, its error(s) will be reported in the status byte of its header (see Receive Packet
Header section).
9.5 Receive Error Processing
Status bits in the receive status register are set to indicate errors associated with packet reception. These errors
are: 1) bus read error, which occurs if the host system attempts to read from an empty receive buffer (this need
never occur if the RX BUF EMPTY bit is checked), 2) short packet error, 3) alignment error (incomplete byte
fragment at end of packet), 4) CRC error and 5) buffer overflow, which occurs if the receive buffer space is
insufficient to hold the entire received packet (the receive controller automatically removes such packets from
the receive buffer and packets already stored in the buffer are not lost). Each of these receive error conditions
may optionally generate an interrupt. None of these errors requires special host processing or intervention, other
than optional tallying of the error for network management purposes.
10. 10BASE-T Transceiver
The MB86967’s transceiver section provides the electrical interface for RJ45 (10BASE-T) connections to the
Ethernet local area network. Its functions include Manchester encoding and decoding of serial data streams to
the transmitter and from the receiver, level conversion, collision detection, signal quality error (SQE) and link
integrity testing, jabber control, loopback, and automatic correction of polarity reversal on the twisted-pair input.
Also provided are outputs for transmit, collision and link test pass LEDs, and compatibility with unshielded
twisted-pair cables. Receive threshold can be reduced to allow an extended range between nodes in low-noise
environments. Programmable functions are controlled via BMPR13. Transceiver status is presented in BMPR15.
10.1 Data Encoder
The encoder converts the serialized NRZ data from the transmitter to Manchester code, the format used on the
network medium. In Manchester code a one is represented as a bit cell (nominally 100-nanoseconds) starting
with a low, ending with a high, with a low-to-high transition at the midpoint; Manchester code for a zero is the
inverse.
The encoder also monitors the state of the internal transmit enable signal from the transmitter section and
appends an end-of-packet symbol (illegal Manchester code) to the data stream when that signal is negated at
the end of the CRC field of the transmitted packet.
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