Fast Ethernet Controller (FEC)
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
18-49
MC, LG, NO, CR, OV and TR bits in the first longword of the buffer descriptor are only modified by the
Ethernet controller when the L bit is set.
Figure 18-27. Receive Buffer Descriptor (RxBD)
Table 18-36. Receive Buffer Descriptor Field Definitions
Word
Location
Field Name
Description
0
Bit 15
E
Empty. Written by the FEC (=0) and user (=1).
0 The data buffer associated with this BD has been filled with received
data, or data reception has been aborted due to an error condition.
The status and length fields have been updated as required.
1 The data buffer associated with this BD is empty, or reception is
currently in progress.
0
Bit 14
RO1
Receive software ownership.
This field is reserved for use by software. This read/write bit is not
modified by hardware nor does its value affect hardware.
0
Bit 13
W
Wrap. Written by user.
0 The next buffer descriptor is found in the consecutive location
1 The next buffer descriptor is found at the location defined in ERDSR.
0
Bit 12
RO2
Receive software ownership.
This field is reserved for use by software. This read/write bit is not
modified by hardware nor does its value affect hardware.
0
Bit 11
L
Last in frame. Written by the FEC.
0 The buffer is not the last in a frame.
1 The buffer is the last in a frame.
0
Bits 10–9
—
Reserved.
0
Bit 8
M
Miss. Written by the FEC. This bit is set by the FEC for frames that were
accepted in promiscuous mode, but were flagged as a miss by the
internal address recognition. Thus, while in promiscuous mode, the user
can use the M-bit to quickly determine whether the frame was destined
to this station. This bit is valid only if the L-bit is set and the PROM bit is
set.
0 The frame was received because of an address recognition hit.
1 The frame was received because of promiscuous mode.
0
Bit 7
BC
Set if the DA is broadcast (FF-FF-FF-FF-FF-FF).
0
Bit 6
MC
Set if the DA is multicast and not BC.
0
2
4
6
Rx Data Buffer Pointer - A[15:0]
Data Length
TR
OV
CR
—
NO
LG
MC
BC
M
—
—
L
RO2
W
RO1
E
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Rx Data Buffer Pointer - A[31:16]
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60
