SPIRIT1 datasheet(60/94 Pages) STMICROELECTRONICS

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Transmission and reception

SPIRIT1

60/94

Doc ID 022758 Rev 3

If the transmitter does not receive any ACK packet when it must, the packet transmitted is

considered lost, and the TX_DATA_SENT in the IRQ_STATUS register remains at 0.

Automatic acknowledgment with piggybacking

The receiver can fill the ACK packet with data. To do so, the receiver must fill the TX FIFO

with the payload it must transmit and the bitfield PIGGYBACKING of PROTOCOL[1] register

must be set.

Automatic retransmission

If the transmitter does not receive the ACK packet, it can be configured to do another

transmission. This operation can be repeated up to 15 times. To configure how many times

this operation must be performed, the field NMAX_RETX of the PROTOCOL[2] register is

used.

9.8

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: payload bytes are continuously read from the TX FIFO and

transmitted without any processing (no preamble, no sync, no coding, etc.). It is the

responsibility of the microcontroller to avoid any underflow conditions on the TX FIFO.

●

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

and transmitted without any processing (no preamble, no sync, no coding, etc.). To

allow the synchronization of an external data source, a data clock signal is also

provided on one of the GPIO ports. Data are sampled by the device on the rising edge

of such clock signal; it is the responsibility of the external data source to provide a

stable input at this edge.

●

3 - PN9 mode: a pseudo-random binary sequence is generated internally. This mode is

provided for test purposes only.

To improve flexibility, the entire packet related functions can be bypassed and the device can

operate in one of the following direct modes, controlled by the field RXMODE of

PCKTCTRL3. In particular:

RXMODE =

●

0 - normal modes

●

1 - direct through FIFO: payload bytes are continuously received and written to the RX

FIFO without any processing (no preamble search, no sync, no decoding, etc.). It is the

responsibility of the microcontroller to avoid any overflow conditions on the RX FIFO.

●

2 - direct through GPIO: payload bits are continuously written to one of the GPIO ports

without any processing (no preamble search, no sync, no decoding, etc.). To allow the

synchronization of an external data sink, a data clock signal is also provided on one of

the GPIO ports. Data are updated by the device on the rising edge of such clock signal

so the MCU must read it during falling edge of CLK.

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