STS1TX datasheet(45/70 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 SYNC

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, 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.

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.

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.

On the receiver, if the field FIX_VAR_LEN of PCKTCTRL2 register is set to 1, the payload

length is directly extracted from the received packet itself; if FIX_VAR_LEN is set to 0, the

payload length is controlled by the PCKTLEN0 and PCKTLEN1 registers as the transmitter.

Furthermore, in variable length mode, the width of the binary field transmitted, where the

actual length of payload is written, must be configured through the field LEN_WIDTH of the

PCKTCTRL3 register according to the maximum length expected in the specific application.

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.

9.6

Data modes

Direct modes are primarily intended to completely bypass all the framer/deframer

operations, in order to give the user maximum flexibility in the choice of frame formats,

controlled by the field TXSOURCE of the PCKTCTRL1 register. In particular:

TXSOURCE =

•

0 - normal modes

•

1 - direct through FIFO: the packet is written in TX FIFO. The user build the packet

according to his need including preamble, payload and soon on. The data are

transmitted without any processing.

•

2 - direct through GPIO: the packet bits are continuously read from one of the GPIO

pins, properly configured, and transmitted without any processing. To allow the

STS1TX 数据表(PDF) 45 Page - STMicroelectronics

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