MRF24XA datasheet(36/258 Pages) MICROCHIP

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MRF24XA

DS70005023C-page 36

Preliminary

 2015 Microchip Technology Inc.

bit 4

TXBUFEMPTY: TX Buffer Empty bit

TXBUFEMPTY = 1 indicates that the Host MCU can safely start writing a new frame to the buffer with-

out overwriting any content that is in use. Writing a single byte to the buffer clears this bit.

TXBUFEMPTY = 0 does not prevent the host from writing further bytes to the buffer. TXBUFEMPTY

is set by the device when transmission is complete.

1 = MCU can safely start writing a new frame to the buffer

0 = Buffer is full, or being written to

When TRXMODE = 00:

Packet mode is configured then TXBUFEMPTY is set at the same time as TXST is cleared and an

interrupt is generated. Therefore, this bit provides no extra information.

When TRXMODE = 10:

TX-Streaming mode is configured then TXBUFEMPTY is set at the same time as one of the buffers

becomes free, while TXST may be set. Therefore, the host MCU uses TXBUFEMPTY to ensure that

the next frame starts loading to the buffers, without overwriting a packet being sent (TXOVFIF).

bit 3

CSMAEN: CSMA-CA Enable bit

This bit enables CSMA-CA algorithm before transmission.

1 = CSMA-CA enabled

0 = CSMA-CA disabled

bit 2-0

DR<2:0>: Transmit Data Rate Field bits

111 = Reserved

110 = 2 Mbps

101 = 1 Mbps

100 = 500 kbps

011 = 250 kbps

010 = 125 kbps

001 = Reserved

000 = Reserved

When transmitting an Auto-ACK frame with Adaptive Data Rate in response to a received frame, the

AckDataRate field in the received frame automatically determines the data rate of the PHY, and not

by this Register field. In all other cases, use this Register field as the current PHY data rate when

transmitting.

The PHY automatically determines the data rate for all received frames regardless of this Register

field and the Adaptive Data Rate Configuration. For more information, refer to Register 2-43.

Note 1: Transmission may include automatic security processing, CRC appending, CSMA-CA channel access,

Acknowledge reception and retransmissions depending on the register Configuration and the Frame Con-

trol field of the frame to be transmitted.

2: DTSM has no relevance in reception as the host can always reconfigure the security material before set-

ting RXDEC.

TXCON (TRANSMIT CONTROL REGISTER) (CONTINUED)

ADDRESS: 0x12

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