14.8.36 XAH_CTRL_0
The XAH_CTRL_0 register is a control register for Extended Operating Mode.
| Name: | XAH_CTRL_0 |
| Offset: | 0x2C |
| Reset: | 0x38 |
| Property: | - |
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| MAX_FRAME_RETRIES[3:0] | MAX_CSMA_RETRIES[2:0] | SLOTTED_OPERATION | |||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | |
Bits 7:4 – MAX_FRAME_RETRIES[3:0] MAX_FRAME_RETRIES
Number of retransmission attempts in TX_ARET mode before the transaction gets cancelled.
| Value | Description |
|---|---|
| 0x3 |
The setting of MAX_FRAME_RETRIES in TX_ARET mode specifies the number of attempts to retransmit a frame, when it was not acknowledged by the recipient, before the transaction gets canceled. Valid values are [0x7, 0x6, …, 0x0]. |
Bits 3:1 – MAX_CSMA_RETRIES[2:0] MAX_CSMA_RETRIES
Number of retries in TX_ARET mode to repeat the CSMA-CA procedure before the transaction gets cancelled.
| Value | Description |
|---|---|
| 0x0(1) | No retries |
| 0x1(1) | One retry |
| 0x2(1) | Two retries |
| 0x3(1) | Three retries |
| 0x4(1) | Four retries |
| 0x5(1) | Five retries |
| 0x6 | Reserved |
| 0x7(2) | Immediate frame transmission without performing CSMA-CA |
- 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 [5, 4, …, 0].
- A value of MAX_CSMA_RETRIES = 7 initiates an immediate frame transmission without performing CSMACA. No retry is performed. This may especially be required for slotted acknowledgment operation.
Bit 0 – SLOTTED_OPERATION SLOTTED_OPERATION
For RX_AACK mode, the register bit SLOTTED_OPERATION determines, if the transceiver will require a time base for slotted operation.
| Value | Description |
|---|---|
| 0x0 | The radio transceiver operates in unslotted mode. An acknowledgment frame is automatically sent if requested. |
| 0x1 | The transmission of an acknowledgment frame has to be controlled by the microcontroller. |
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 has to be initiated by the microcontroller using the rising edge of pin 11 (SLP_TR). This waiting state is signaled in register bits TRAC_STATUS (register 0x02, TRX_STATE) with value SUCCESS_WAIT_FOR_ACK.