MT7620 PROGRAMMING GUIDE
Integrated 802.11n MAC/BBP and 2.4 GHz RF/FEM Router-on-a-Chip
4. Tx/Rx Descriptors and Wireless Information
4.1 Tx Descriptors and Frame Information
To transmit a frame, the driver needs to prepare the Tx frame information for hardware. The Tx frame
information contains the transmission control, the header, and the payload. The transmission control
information (TXWI) is used by the MAC and BBP and is applied to the associated Tx frame on transmission. The
header and payload is the content of an 802.11 packet.
The Tx information may be divided into several segments. The Tx descriptor (TXD) specifies the location and
length of the Tx frame information segments. Tx frame information may be linked by use of several TXD. These
TXD are arranged in a TXD ring in serial.
The diagram below illustrates the relationship between TXD and Tx frame information.
TXD[k] SDP1
SDL1, LS1=1
TXD[k] SDP0
SDL0, LS1=0
….
TXD[1] SDP1
SDL1, LS1=0
TXD[1] SDP0
SDL0, LS1=0
TXD[0] SDP1
SDL1, LS1=0
TXD[0] SDP0
SDL0, LS0=0
TXD for Tx
frame i
Tx Payload
(segment k)
….
Tx Payload
(segment 2)
….
Tx Payload
(segment 1)
….
Tx Payload
(segment 0)
….
802.11 Header
TXWI (4 DW)
TXD[0].SDP0
TXD[0].SDP1
TXD[1].SDP0
TXD[1].SDP1
TXD[k].SDP1
Tx Ring
Figure 4-1 TXD and Tx Frame Information
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