AT86RF231 datasheet(21/180 Pages) ATMEL

21 / 180 page

8111A–AVR–05/08

AT86RF231

Note, the Frame Buffer read access can be terminated at any time without any consequences by

setting /SEL = H, e.g. after reading the PHR byte only.

On Frame Buffer write access the second byte transferred on MOSI contains the frame length

(PHR field) followed by the payload data (PSDU) as shown by Figure 6-8 on page 21.

Figure 6-8.

Packet Structure - Frame Write Access

The number of bytes n for one frame access is calculated as follows:

The maximum value of frame_length is 127 bytes. That means that n

≤ 130 for Frame Buffer

read and n

≤ 129 for Frame Buffer write accesses.

Each read or write of a data byte increments automatically the address counter of the Frame

Buffer until the access is terminated by setting /SEL = H. A Frame Buffer read access may be

terminated (/SEL = H) at any time without affecting the Frame Buffer content. Another Frame

Buffer read operation starts again at the PHR field.

The content of the Frame Buffer is only overwritten by a new received frame or a Frame Buffer

write access.

Figure 6-9 on page 21 and Figure 6-10 on page 22 illustrate an example SPI sequence of a

Frame Buffer access to read and write a frame with 4-byte PSDU respectively.

Figure 6-9.

Example SPI Sequence - Frame Buffer Read of a Frame with 4-byte PSDU

reserved[5:0]

MOSI

PHY_STATUS

MISO

byte 1 (command byte)

PHR[7:0]

byte 2 (data byte)

PSDU[7:0]

byte 3 (data byte)

PSDU[7:0]

byte n-1 (data byte)

PSDU[7:0]

byte n (data byte)

• Read Access:

n = 3 + frame_length

[PHY_STATUS, PHR byte, PSDU data, and LQI byte]

• Write Access:

n = 2 + frame_length

[command byte, PHR byte, and PSDU data]

COMMAND

PHY_STATUS

PHR

PSDU 2

PSDU 1

PSDU 4

PSDU 3

LQI

SCLK

MOSI

MISO

/SEL

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