STS1TX datasheet(43/70 Pages) STMICROELECTRONICS

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STS1TX

Transmission and reception

Preamble (programmable field): the length of the preamble is programmable from 1 to 32

bytes by the PREAMBLE_LENGTH field of the PCKTCTRL2 register. Each preamble byte is

a '10101010' binary sequence.

Sync (programmable field): the length of the synchronization field is programmable (from 1

to 4 bytes) through dedicated registers. The SYNC word is programmable through registers

SYNC1, SYNC2, SYNC3, and SYNC4. If the programmed sync length is 1 then only the

SYNC1 word is transmitted; if the programmed sync length is 2 then only SYNC1 and

SYNC2 words are transmitted and so on.

Length (programmable/optional field): the packet length field is an optional field that is

defined as the cumulative length of Address (2 bytes always), Control, and Payload fields. It

is possible to support fixed and variable packet length. In fixed mode, the field length is not

used.

Destination address (programmable/optional field): is filled with the value of register

TX_DEST_ADDR.

Source address (programmable field): is filled with the value of register

TX_SOURCE_ADDR. The field ADDRESS_LEN of the PCKTCTRL4 register must be set

always to 2.

Control (programmable/optional field): is programmable from 0 to 4 bytes through the

CONTROL_LEN field of the PCKTCTRL4 register. Control fields of the packet can be set

using the TX_CTRL_FIELD[3:0] register.

Sequence number (programmable field): is a 2-bit field and contains the sequence number

of the transmitted packet. It is incremented automatically every time a new packet is

transmitted. It can be re-loaded with the value in the TX_SEQ_NUM_RELOAD[1:0] field of

the PROTOCOL[2] register, by using the SEQUENCE_UPDATE command.

NO_ACK (programmable field): It is programmed by the bit field NACK_TX of the register

PROTOCOL[0]. It is important set to 0 the bit field in the others packet formats.

Payload (programmable/optional field): the device supports both fixed and variable payload

length transmission from 0 to 65535 bytes.

On the transmitter, the payload length is always set as: PCKTLEN1 × 256 + PCKTLEN0.

In variable length mode, the width of the binary field transmitted, where the actual length of

payload is written, can be configured through the field LEN_WIDTH of the PCKTCTRL3

Example 1

•

If the variable payload length is from 0 to 31 bytes, then LEN_WIDTH = 5

•

If the variable payload length is from 0 to 255 bytes, then LEN_WIDTH = 8

•

If the variable payload length is from 0 to 65535 bytes, then LEN_WIDTH = 16.

CRC (programmable/optional field): There are different polynomials CRC: 8 bits, 16 bits (2

polynomials are available) and 24 bits.

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