64
8168C-MCU Wireless-02/10
AT86RF212
Bit
3
2
1
0
Name
MAX_CSMA_RETRIES[2:0]
SLOTTED_OPERATION
Read/Write
R/W
Reset Value
1
0
Bit 7:4 – MAX_FRAME_RETRIES
The setting of MAX_FRAME_RETRIES specifies the number of attempts in TX_ARET
mode to automatically retransmit a frame when it was not acknowledged by the
recipient.
Bit 3:1 – MAX_CSMA_RETRIES
MAX_CSMA_RETRIES specifies the number of retries in TX_ARET mode to repeat the
CSMA-CA
procedure
before
the transaction gets
cancelled.
According
to
IEEE 802.15.4, the valid range of MAX_CSMA_RETRIES is [0, 1, … , 5].
A value of MAX_CSMA_RETRIES = 7 initiates an immediate frame transmission
without performing CSMA-CA. No retry is performed. This may especially be required
for slotted acknowledgement operation. MAX_CSMA_RETRIES = 6 is reserved.
Bit 0 – SLOTTED_OPERATION
If set, register bit SLOTTED_OPERATION enables RX_AACK acknowledgment
generation in slotted operation mode, refer to section
5.2.3.5.Using RX_AACK mode in networks operating in beacon or slotted mode (refer to
IEEE 802.15.4-2006, section 5.5.1), register bit SLOTTED_OPERATION indicates that
acknowledgement frames are to be sent on backoff slot boundaries (slotted
acknowledgement).
If this register bit is set, the acknowledgement frame transmission is initiated by the
microcontroller using the rising edge of pin 11 (SLP_TR).
Register 0x2D (CSMA_SEED_0):
The CSMA_SEED_0 register is a control register for TX_ARET and contains a part of
the CSMA seed for the CSMA-CA algorithm.
Table 5-26. Register 0x2D (CSMA_SEED_0)
Bit
7
6
5
4
3
2
1
0
Name
CSMA_SEED[7:0]
Read/Write
R/W
Reset Value
1
0
1
0
1
0
Bit 7:0 – CSMA_SEED
This register contains the lower 8 bit of the CSMA_SEED, i.e. bits [7:0]. The higher 3 bit
are part of register bits CSMA_SEED_1 (register 0x2E, CSMA_SEED_1).
CSMA_SEED is the seed for the random number generation that determines the length
of the backoff period in the CSMA-CA algorithm.
It is recommended to initialize registers CSMA_SEED with random values. This can be
done using register bits RND_VALUE (register 0x06, PHY_RSSI), refer to section
9.2.The content of register CSMA_SEED_0/1 initializes the TX_ARET random backoff
generator after wakeup from SLEEP state. It is recommended to reinitialize both
registers before every SLEEP state with a random value.