Freescale Semiconductor MPC8260 - Manual (Page 794)

SCC Ethernet Mode
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
25-10 Freescale Semiconductor
Table 25-3 describes receive commands.
NOTE
After a CPM reset via CPCR[RST], the Ethernet transmit enable (TENA)
signal defaults to its RTS, active-low functionality. To prevent false TENA
assertions to an external transceiver, configure TENA as an input before
issuing a CPM reset. See step 3 in
Section 25.21, “SCC Ethernet
Programming Example.”
Table 25-2. 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 ensure that transmission stops smoothly after the current frame finishes or has a collision.
SCCE[GRA] is set once transmission stops, at which point Ethernet transmit parameters and their BDs
can be updated. TBPTR points to the next TxBD. Transmission begins once the R bit of the next BD is
set and a
RESTART TRANSMIT command is issued.
Note that if GRACEFUL STOP TRANSMIT is issued and the current frame ends in a collision, TBPTR points
to the start of the collided frame with the R bit still set in the BD. The frame looks as if it was never sent.
RESTART
TRANSMIT
Enables transmission of characters on the transmit channel. The Ethernet controller expects it after a
GRACEFUL STOP TRANSMIT command is issued or a transmitter error. The Ethernet controller resumes
transmission from the current TBPTR in the channel TxBD table.
INIT TX
PARAMETERS
Initializes transmit parameters in this serial channel parameter RAM to reset state. Issue only when the
transmitter is disabled.
INIT TX and RX PARAMETERS resets both transmit and receive parameters.
Table 25-3. Receive Commands
Command Description
ENTER HUNT
MODE
After hardware or software is reset and the channel is enabled in GSMR_L, the channel is in receive
enable mode and uses the first BD in the table. The receiver then enters hunt mode, waiting for an
incoming frame. The
ENTER HUNT MODE command is generally used to force the Ethernet receiver to
stop receiving the current frame and enter hunt mode, in which the Ethernet controller continually scans
the input data stream for a transition of carrier sense from inactive to active and then a preamble
sequence followed by the start frame delimiter. After receiving the command, the buffer is closed and
the CRC calculation is reset. The next RxBD is used to receive more frames.
CLOSE RXBD Should not be used with the Ethernet controller.
INIT RX
PARAMETERS
Initializes receive parameters in this serial channel parameter RAM to their reset state. Issue it only
when the receiver is disabled.
INIT TX and RX PARAMETERS resets receive and transmit parameters.
SET GROUP
ADDRESS
Used to set one of the 64 bits of the four individual/group address hash filter registers. The address to
be added to the hash table should be written to TADDR_L, TADDR_M, and TADDR_H in the parameter
RAM before executing this command. The CP uses an individual address if the I/G bit in the address
stored in TADDR is 0; otherwise, it uses a group address. This command can be executed at any time,
regardless of whether the Ethernet channel is enabled.
To delete an address from the hash table, disable the Ethernet channel, clear the hash table registers,
and execute this command for the remaining addresses. Do not simply clear the channel’s associated
hash table bit because the hash table may have multiple addresses mapped to the same hash table bit.