NRF52820-QDAA-R datasheet(185/437 Pages) NORDIC

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Peripherals

Long frame

ACK

tack = 32 symbols

Short frame

ACK

tack = 32 symbols

tlifs = 40 symbols

tsifs = 12 symbols

Acknowledged transmission

Long frame

Short frame

tlifs = 40 symbols

tsifs = 12 symbols

Unacknowledged transmission

Figure 75: Interframe spacing examples

6.12.14 EasyDMA

The RADIO uses EasyDMA to read and write packets to RAM without CPU involvement.

As illustrated in RADIO block diagram on page 163, the RADIO's EasyDMA utilizes the same PACKETPTR

for receiving and transmitting packets. This pointer should be reconfigured by the CPU each time before

RADIO is started by the START task. The PACKETPTR register is double-buffered, meaning that it can be

updated and prepared for the next transmission.

The END event indicates that the last bit has been processed by the RADIO. The DISABLED event is issued

to acknowledge that a DISABLE task is done.

The structure of a packet is described in detail in Packet configuration on page 163. The data that is

stored in Data RAM and transported by EasyDMA consists of the following fields:

• S0

• LENGTH

• S1

• PAYLOAD

In addition, a static add-on is sent immediately after the payload.

The size of each of the above fields in the frame is configurable (see Packet configuration on page 163),

and the space occupied in RAM depends on these settings. The size of the field can be zero, as long as the

resulting frame complies with the chosen RF protocol.

All fields are extended in size to align with a byte boundary in RAM. For instance, a 3-bit long field on air

will occupy 1 byte in RAM while a 9-bit long field will be extended to 2 bytes.

The packet's elements can be configured as follows:

• CI, TERM1, and TERM2 fields are only present in Bluetooth® Low Energy Long Range mode

• S0 is configured through the PCNF0.S0LEN field

• LENGTH is configured through the PCNF0.LFLEN field

• S1 is configured through the PCNF0.S1LEN field

• Payload size is configured through the value in RAM corresponding to the LENGTH field

• Static add-on size is configured through the PCNF1.STATLEN field

The PCNF1.MAXLEN field configures the maximum packet payload plus add-on size in number of bytes

that can be transmitted or received by the RADIO. This feature can be used to ensure that the RADIO does

not overwrite, or read beyond, the RAM assigned to the packet payload. This means that if the LENGTH

field of the packet payload exceedes PCNF1.STATLEN, and the LENGTH field in the packet specifies a

packet larger than configured in PCNF1.MAXLEN, the payload will be truncated to the length specified in

PCNF1.MAXLEN.

4463_156 v1.0

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