STS1TX datasheet(47/70 Pages) STMICROELECTRONICS

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STS1TX

Transmission and reception

The FIFO almost empty event occurs when the data crosses the threshold from above to

below. The TX FIFO almost full threshold can be configured using the field TXAFTHR in the

FIFO_CONFIG[1] register.

Another event occurs when the FIFO goes into overflow or underflow.

The overflow happens when the data in the FIFO are more than 96 bytes. The underflow

happens when the STS1TX accesses the FIFO locations to read data, but there is no data

present.

For example:

•

If it sends more data than the actual number of bytes in the TX FIFO, the TX FIFO

underflow/overflow error occurs for an underflow event.

•

If it writes more than 96 bytes in the TX FIFO, a TX FIFO underflow/overflow error

occurs for an overflow event.

An easy way to clean the FIFOs is to use the flush command: FLUSHTXFIFO

The write TX FIFO operation needs an extra SPI transaction to write correctly the last byte

into the TX FIFO. Usually, this last SPI transaction is generated from the TX command sent

to transmit the data, otherwise a dummy SPI transaction must be done.

Using the auto-retransmission feature of the STS1TX (packet format STack), if the packet is

more than 96 bytes, the packet must be reloaded into the TX FIFO by the MCU. However, if

the payload is 96 bytes or less, the STS1TX handles the payload and it is not necessary to

reload the data into the TX FIFO at each retransmission.

9.8

Frequency hopping

In order to ensure good link reliability in an interference corrupted scenario, the device

supports frequency hopping, managed by the MCU; in particular, the STS1TX supports slow

frequency hopping, meaning that the systems change frequency at a rate slower than the

information rate.

Depending on the desired blanking interval (the time during a hop), frequency hopping can

be done by performing the complete PLL calibration for each channel hop, or reading in the

suitable register calibration data calculated at startup and stored in the non-volatile memory

of the MCU. The former solution gives a long blanking interval but is more robust compared

with supply voltage and temperature variation. The latter provides a shorter blanking time

but is sensitive to voltage and temperature variation and requires memory space to store

calibration data for each channel involved in hopping.

STS1TX 数据表(PDF) 47 Page - STMicroelectronics

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