SPIRIT1 datasheet(59/94 Pages) STMICROELECTRONICS

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SPIRIT1

Transmission and reception

Doc ID 022758 Rev 3

59/94

More than one automatic filtering option can be enabled at the same time.

Source address: the received packet is discarded if the source address received does not

match the programmed source address reference through the source mask address (the

reference value used for the comparison is the reference one in AND bitwise with the source

mask). The source address reference can be programmed for the receiver in the

RX_SOURCE_ADDR register and the source address mask in the RX_SOURCE_MASK

PCKT_FLT_OPTIONS register must be set.

Control: the received packet is discarded if the control field received does not match the

programmed control reference through the control mask (the reference value used for the

comparison is the reference one in AND bitwise with the control mask). The control

reference can be programmed for the receiver in the CONTROLx_FIELD registers and the

control field mask in the CONTROLx_MASK registers. To enable this automatic filtering

option the bitfield CONTROL_FILTERING of the PCKT_FLT_OPTIONS register must be

set.

When a filtering mechanism is enabled the packet is signaled to the MCU only if the check is

positive, otherwise the packet is automatically discarded.

9.7.5

Link layer protocol

SPIRIT1 has an embedded auto-ACK and auto-retransmission available through the STack

packet format.

Automatic acknowledgment

Automatic acknowledgment is enabled on the receiver by setting the bitfield AUTO_ACK of

the PROTOCOL register. In this way, after the receiver receives a packet with success, it

sends an ACK packet only if the NO_ACK bit of the received packet is 1. This gives an

opportunity for the transmitter to tell the receiver if the packet sent must be acknowledged or

not. The ACK request can be put in the packet (NO_ACK packet's bitfield at 1) by setting the

NACK_TX field of the PROTOCOL[2] register.

If the ACK request is ON (NO_ACK packet's bitfield at 1), the transmitter stays in RX state to

receive an ACK packet until the RX timeout, programmed with the

RX_TIMEOUT_PRESCALER and RX_TIMEOUT_COUNTER, expires.

Table 30.

Packet configuration

STack

MBUS

Basic

Destination address filtering

Optional

Broadcast and multicast

addressing

Optional

Source address filtering

Optional

Custom filtering

Optional

CRC filtering

Optional

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