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Fast Ethernet Controllers (FEC0 and FEC1)
26-33
Freescale Semiconductor
buffer is complete. In the TxBD, the user initializes the R, W, L, and TC bits and the length (in bytes) in
the first longword and the buffer pointer in the second longword.
The FEC clears the R bit when the buffer is transferred. Status bits for the buffer/frame are not included in
the transmit buffer descriptors. Transmit frame status is indicated via individual interrupt bits (error
conditions) and in statistic counters in the MIB block. See
Section 26.4.1, “MIB Block Counters Memory
for more details.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
R
TO1
W
TO2
L
TC
ABC
—
—
—
—
—
—
—
—
—
2
Data Length
4
Tx Data Buffer Pointer - A[31:16]
6
Tx Data Buffer Pointer - A[15:0]
Figure 26-26. Transmit Buffer Descriptor (TxBD
n
)
Table 26-30. Transmit Buffer Descriptor Field Definitions
Word
Field
Description
0
15
R
Ready. Written by the FEC and you.
0 The data buffer associated with this BD is not ready for transmission. You are free to manipulate
this BD or its associated data buffer. The FEC clears this bit after the buffer has been transmitted
or after an error condition is encountered.
1 The data buffer, prepared for transmission by you, has not been transmitted or currently transmits.
You may write no fields of this BD after this bit is set.
0
14
TO1
Transmit software ownership. This field is reserved for software use. This read/write bit is not modified
by hardware nor does its value affect hardware.
0
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 ETDSR.
n
0
12
TO2
Transmit 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
11
L
Last in frame. Written by user.
0 The buffer is not the last in the transmit frame
1 The buffer is the last in the transmit frame
0
10
TC
Transmit CRC. Written by user (only valid if L is set).
0 End transmission immediately after the last data byte
1 Transmit the CRC sequence after the last data byte
0
9
ABC
Append bad CRC. Written by user (only valid if L is set).
0 No effect
1 Transmit the CRC sequence inverted after the last data byte (regardless of TC value)
0
8–0
Reserved, must be cleared.
2
15–0
Data
Length
Data length, written by user.
Data length is the number of octets the FEC should transmit from this BD’s data buffer. It is never
modified by the FEC.
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...