User's Manual

RTL8187B
Datasheet
Wireless LAN Network Interface Controller
29
Track ID: JATR-1076-21 Rev. 1.0
11.2. Rx Command
The RTL8187B supports an Rx command queue to feedback the Tx state and beacon interrupt . When the
Command Type (bit[31:30]) is set to 00b, it indicates Tx Beacon Interrupt. When set to 01b, it indicates Tx
Close Descriptor.
Table 31. Tx Beacon Interrupt
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Cmd
Type
RSVD Last Beacon CW
Last Beacon TSF[31:0]
Table 32. Tx Close Descriptor
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Cmd
Type
FS LS Sequence No[11:0] T
O
K
RTS Retry Count[6:0] Packet Retry Count[7:0]
MAC Used Time [15:0]
11.3. Loopback Operation
Loopback mode is normally used to verify that the logic operations have performed correctly. In loopback
mode, the RTL8187B takes frames from the transmit descriptor and transmits them up to internal Rx logic.
The loopback function does not apply to an external PHYceiver.
11.4. Tx Encapsulation (With RTL8187B Internal Baseband
Processor)
When operating in Tx mode, the RTL8187B encapsulates the frames that it transmits according to the
Differential Binary Phase Shift Keying (DBPSK) for 1Mbps, Differential Quaternary Phase Shift Keying
(DQPSK) for 2Mbps, and Complementary Code Keying (CCK) for 5.5Mbps and 11Mbps modulators. The
changes to the original packet data are as follows:
1. The PLCP preamble is always transmitted as the DBPSK waveform and used by the receiver to achieve
initial PN synchronization.
2. The PLCP header can be configured to be either DBPSK or DQPSK and includes the necessary data
fields of the communications protocol to establish the physical layer link.
3. The MAC frame can be configured for DBPSK, DQPSK, or CCK.