LLCC68 datasheet(44/106 Pages) SEMTECH

44 / 106 page

LLCC68

Data Sheet

Rev. 1.0

DS.LLCC68.W.APP

July 2019

44 of 106

Semtech

www.semtech.com

7.2 Data Buffer in Receive Mode

In receive mode RxBaseAddr specifies the buffer offset in memory at which the received packet payload data will be written.

The buffer offset of the last byte written in receive mode is then stored in RxDataPointer which is initialized to the value of

RxBaseAddr at the beginning of the reception.

The pointer to the first byte of the last packet received and the packet length can be read with the command

GetRxbufferStatus().

In single mode, RxDataPointer is automatically initialized to RxBaseAddr each time the transceiver enters Rx mode. In

continuous mode the pointer is incremented starting from the previous position.

7.3 Data Buffer in Transmit Mode

Upon each transition to transmit mode TxDataPointer is initialized to TxBaseAddr and is incremented each time a byte is sent

over the air. This operation stops once the number of bytes sent equals the payloadlength parameter as defined in the

function SetPacketParams(...).

7.4 Using the Data Buffer

Both, RxBaseAddr and TxBaseAddr are set using the command SetBufferBaseAddresses(...).

By default RxBaseAddr and TxBaseAddr are initialized at address 0x00.

Due to the contiguous nature of the data buffer, the base addresses for Tx and Rx are fully configurable across the 256-byte

memory area. Each pointer can be set independently anywhere within the buffer. To exploit the maximum data buffer size

in transmit or receive mode, the whole data buffer can be used in each mode by setting the base addresses TxBaseAddr and

RxBaseAddr at the bottom of the memory (0x00).

The data buffer is cleared when the device is put into Sleep mode (implying no access). The data is retained in all other

modes of operation.

The data buffer is acceded via the command WriteBuffer(...) and ReadBuffer(...). In this function the parameter offset defines

the address pointer of the first data to be written or read. Offset zero defines the first position of the data buffer.

Before any read or write operation it is hence necessary to initialize this offset to the corresponding beginning of the buffer.

Upon reading or writing to the data buffer the address pointer will then increment automatically.

Two possibilities exist to obtain the offset value:

•

First is to use the RxBaseAddr value since the user defines it before receiving a payload.

•

Second, offset can be initialized with the value of RxStartBufferPointer returned by GetRxbufferStatus(...) command.

Note:

All the received data will be written to the data buffer even if the CRC is invalid, permitting user-defined post processing of

corrupted data. When receiving, if the packet size exceeds the buffer memory allocated for the Rx, it will overwrite the

transmit portion of the data buffer.

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