MPC8280 datasheet(1247/1386 Pages) FREESCALE

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Fast Ethernet Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

36-13

Receive commands that apply to Ethernet are described in Table 36-4.

If an address from the hash table must be deleted, the Ethernet channel must be disabled, the hash table

registers must be cleared, and the SET GROUP ADDRESS command must be executed for the remaining

preferred addresses. This is required because the hash table might have mapped multiple addresses to the

same hash table bit.

Table 36-3. Transmit Commands

Command

Description

STOP

TRANSMIT

When used with the Ethernet controller, this command violates a specific behavior of an Ethernet/IEEE

802.3 station. It should not be used.

GRACEFUL

STOP

TRANSMIT

Used to smoothly stop transmission after the current frame finishes sending or undergoes a collision

(immediately if there is no frame being sent). FCCE[GRA] is set once transmission stops. Then the

Ethernet transmit parameters (including BDs) can be modified by the user. The TBPTR points to the

next TxBD in the table. Transmission begins when the R bit of the next BD is set and the RESTART

TRANSMIT

command is issued. Note that if the GRACEFUL STOP TRANSMIT command is issued and the

current transmit frame ends in a collision, the TBPTR points to the beginning of the collided frame with

TxBD[R] still set (the frame looks as if it was never sent).

RESTART

TRANSMIT

Enables transmission of characters on the transmit channel. It is expected by the Ethernet controller

after a GRACEFUL STOP TRANSMIT command or transmitter error (underrun, retransmission limit reached,

or late collision). The Ethernet controller resumes transmission from the current TBPTR in the channel

TxBD table.

INIT TX

PARAMETERS

Initializes all the transmit parameters in this serial channel parameter RAM to their reset state. This

command should be issued only when the transmitter is disabled. Note that the INIT TX AND RX

PARAMETERS

command can also be used to reset the transmit and receive parameters.

Table 36-4. Receive Commands

Command

Description

ENTER HUNT

MODE

After the hardware or software is reset and the channel in the FCC mode register is enabled, the

channel is in the receive enable mode and uses the first BD in the table. This command is generally

used to force the Ethernet receiver to abort reception of the current frame and enter hunt mode. In hunt

mode, the Ethernet controller continually scans the input data stream for a transition of carrier sense

from inactive to active followed by a preamble sequence and the start frame delimiter. After receiving

the command, the current receive buffer is closed, the error status flags and length field are cleared,

RxBD[E] (the empty bit) is set, and the CRC calculation is reset. Further frame reception uses the

current RxBD.

Note that short frames pending in the internal FIFO may be lost.

INIT RX

PARAMETERS

Initializes all the receive parameters in this serial channel parameter RAM to their reset state and

should only be issued when the receiver is disabled. Note that the INIT TX AND RX PARAMETERS

command can also be used to reset the receive and transmit parameters.

SET GROUP

ADDRESS

Used to set one of the 64 bits of the four individual/group address hash filter registers (GADDR[1–4]

or IADDR[1–4]). The individual or group address (48 bits) to be added to the hash table should be

written to TADDR_L, TADDR_M, and TADDR_H in the parameter RAM prior to executing this

command. The CP checks the I/G bit in the address stored in TADDR to determine whether to use the

individual hash table or the group hash table. A 0 in the I/G bit indicates an individual address; 1

indicates a group address. This command can be executed at any time, regardless of whether the

Ethernet channel is enabled.

MPC8280 Datasheet(PDF) 1247 Page - Freescale Semiconductor, Inc

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