Fast Ethernet Controller (FEC)
MPC5566 Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 15-49
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0 1 2 3456 7 8 91011121314 15
Offset + 0 R TO1 W TO2 L TC ABC — — — — — — — — —
Offset + 2 Data Length
Offset + 4 Tx Data Buffer Pointer - A [0:15]
Offset + 6 Tx Data Buffer Pointer - A [16:31]
Figure 15-31. Transmit Buffer Descriptor (TxBD)
Table 15-37. Transmit Buffer Descriptor Field Definitions
Halfword Location Field Name Description
Offset + 0 Bit 0 R Ready. Written by the FEC and the application.
0 The data buffer associated with this BD is not ready for
transmission. the application can 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, which has been prepared for transmission
by the application, has not been transmitted or is currently
being transmitted. No fields of this BD can be written by the
application once this bit is set.
Offset + 0 Bit 1 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.
Offset + 0 Bit 2 W Wrap. Written by the application.
0 The next buffer descriptor is found in the consecutive
location
1 The next buffer descriptor is found at the location defined in
ETDSR.
Offset + 0 Bit 3 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.
Offset + 0 Bit 4 L Last in frame. Written by the application.
0 The buffer is not the last in the transmit frame.
1 The buffer is the last in the transmit frame.
Offset + 0 Bit 5 TC Tx CRC. Written by the application (only valid if L = 1).
0 End transmission immediately after the last data byte.
1 Transmit the CRC sequence after the last data byte.
Offset + 0 Bit 6 ABC Append invalid CRC. Written by the application
(only valid if L = 1).
0 No effect
1 Transmit the CRC sequence inverted after the last data byte
(regardless of TC value).
Offset + 0 Bits [7:15] — Reserved.
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