ST25R3911B datasheet(22/116 Pages) STMICROELECTRONICS

22 / 116 page

Figure 12. SPI communication: reading a single byte

SCLK rising edge

Data transferred from MCU

SCLK falling edge

Data is sampled

/SS raising

edge

indicates end

of Read mode

Two leading bits

indicate Mode

/SS

SCLK

MOSI

tristate

MISO

SCLK rising edge

Data moved from

Address A5-A0

SCLK falling edge

Data transferred to MCU

Loading transmitting data into FIFO

Loading the transmitting data into the FIFO is similar to writing data into an addressable registers. Difference is

that in case of loading more bytes all bytes go to the FIFO. SPI operation mode bits 10 indicate FIFO operations.

In case of loading transmitting data into FIFO all bits <C5 – C0> are set to 0. Then a bit-stream, the data to be

sent (1 to 96 bytes), can be transferred. In case the command is terminated by putting /SS high before a packet of

8 bits (one byte) is sent, writing of that particular byte in FIFO is not performed.

Figure 13 shows how to load the Transmitting Data into the FIFO.

Figure 13. SPI communication: loading of FIFO

SCLK rising edge

Data transferred from MCU

SCLK falling edge

Data is sampled

/SS raising

edge

indicates

end of

FIFO Mode

/SS

SCLK

MOSI

10 pattern

indicates

FIFO Mode

1 to 96

bytes

Start of

paylod data

Reading received data from FIFO

Reading received data from the FIFO is similar to reading data from an addressable registers. Difference is that in

case of reading more bytes they all come from the FIFO. SPI operation mode bits 10 indicate FIFO operations. In

case of reading the received data from the FIFO all bits <C5 – C0> are set to 1. On the following SCLK rising

edges the data from FIFO appears as in case of read data from addressable registers. If the command is

terminated by putting /SS high before a packet of 8 bits (one byte) is read, that particular byte is considered

unread and will be the first one read in next FIFO read operation.

ST25R3911B

Application information

DS11793 - Rev 6

page 22/116

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