ST25R3918 datasheet(48/141 Pages) STMICROELECTRONICS

48 / 141 page

Application information

ST25R3918

48/141

DS13490 Rev 2

Reading received data from FIFO

Reading received data from the FIFO is similar to reading data from an addressable

registers. The SPI sequence starts with SPI operation mode bits ‘10’ to indicate a FIFO

operation followed by <C5:C0> set to 011111b. After the mode byte the ST25R3918 will

output the data from the FIFO as long as SCLK is present and BSS is kept low.

Figure 14. SPI communication: FIFO reading

Direct command mode

Direct command mode has no arguments, so a single byte is sent. The byte starts with the

SPI operation mode bits ‘11’ to indicate Direct Command Mode followed by the direct

command code (see Table 11) in <C5:C0>, MSB first. Execution of the direct command

starts with the rising edge of BSS (see Figure 15).

While the execution of some direct commands is immediate, there are others that start a

process of certain duration (e.g. calibration, measurements). During the execution of such

commands it is not allowed to start another activity over the SPI interface, an IRQ is sent.

when the execution is terminated.

MS53128V1

SCLK rising edge

Data transferred from MCU

SCLK falling edge

Data is sampled

BSS raising

edge indicates

end of FIFO

mode

10 pattern

indicates

FIFO mode

tristate

BSS

SCLK

MOSI

MISO

SCLK rising edge

Data moved from FIFO

SCLK falling edge

Data transferred to MCU

1 to 512

bytes

ST25R3918 Datasheet(PDF) 48 Page - STMicroelectronics

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