HS_Media independent interface (MII)
RM0082
510/844
Doc ID 018672 Rev 1
Figure 52.
DMA descriptor format (Transmit Descriptor, 32 bit)
Table 414.
Transmit descriptor 0 (TDES0)
Bit
Name
Description
[31]
OWN
Own Bit. If set, indicates that the descriptor is owned by the DMA of MAC. If
cleared, the descriptor is owned by the host.
[30]
IC
Interrupt on Completion. Setting this bit, the TI bit of the Status register (DMA
Register5) is set after the present frame has been transmitted.
[29]
LS
Last Segment. If set, it indicates that the buffer contains the last segment of
the frame.
[28]
FS
First Segment. If set, it indicates that the buffer contains the first segment of
the frame.
[27]
DC
Disable CRC. Setting this bit, the MAC doesn’t automatically add padding to
a framer shorter than 64 bytes.
[26]
DP
Disable Padding. Setting this bit, the MAC doesn’t automatically add padding
to a frame shorter than 64 bytes.
If cleared, the DMA automatically adds padding and CRC to a frame shorter
that 64 bytes and the CRC field is added despite the state if the DC bit
(TDES0[27]). Valid only if (TDES0[28]) is set.
[25]
TTSE
Reserved
[24]
Reserved
-
[23:22]
CIC
Checksum Insertion Control. These bits control the checksum calculation
and insertion. Bit encodings are as shown below.
2’b00: Checksum Insertion Disabled.
2’b01: Only IP header checksum calculation and insertion are enabled.
2’b10: IP Header checksum and payload checksum calculation and insertion
are enabled, but pseudo-header checksum is calculated in hardware.
2’b11: IP Header checksum and payload checksum calculation and insertion
are enabled, and pseudo-header checksum is calculated in hardware.
[21]
TER
Transmit End of Ring. If set, it indicates that the descriptor list reached its
final descriptor. The DMA returns to the base address of the list, creating a
descriptor ring structure.
O
W
N
TDES0
TDES1
TDES2
TDES3
Ctrl
[30:26]
Reserved
[25:24]
Ctrl
[23:20]
Reserved
[19:17]
Status [16:0]
Reserved
[31:29]
Buffer 2 Byte Count
[28:16]
Reserved
[15:13]
Buffer 2 Byte Count
[12:0]
Buffer 1 Address [31:0]
Buffer 2 Address [31:0] or Next Descriptor Address [31:0]
0
31