ST72324BJ2 datasheet(112/188 Pages) STMICROELECTRONICS

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On-chip peripherals

ST72324B

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Receiver muting and wake-up feature

In multiprocessor configurations it is often desirable that only the intended message

recipient should actively receive the full message contents, thus reducing redundant SCI

service overhead for all non-addressed receivers.

The non-addressed devices may be placed in sleep mode by means of the muting function.

Setting the RWU bit by software puts the SCI in sleep mode:

All the reception status bits cannot be set.

All the receive interrupts are inhibited.

A muted receiver may be awakened by one of the following two ways:

●

by Idle Line detection if the Wake bit is reset,

●

by Address Mark detection if the Wake bit is set.

A receiver wakes up by Idle Line detection when the Receive line has recognized an Idle

Frame. Then the RWU bit is reset by hardware but the Idle bit is not set.

A receiver wakes up by Address Mark detection when it received a ‘1’ as the most significant

bit of a word, thus indicating that the message is an address. The reception of this particular

word wakes up the receiver, resets the RWU bit and sets the RDRF bit, which allows the

receiver to receive this word normally and to use it as an address word.

Caution:

In Mute mode, do not write to the SCICR2 register. If the SCI is in Mute mode during the

read operation (RWU = 1) and an address mark wake-up event occurs (RWU is reset)

before the write operation, the RWU bit will be set again by this write operation.

Consequently the address byte is lost and the SCI is not woken up from Mute mode.

Parity control

Parity control (generation of parity bit in transmission and parity checking in reception) can

be enabled by setting the PCE bit in the SCICR1 register. Depending on the frame length

defined by the M bit, the possible SCI frame formats are as listed in Table 58.

Table 58.

Frame formats(1)(2)

SB = Start bit, STB = Stop bit, and PB = Parity bit.

In case of wake-up by an address mark, the MSB bit of the data is taken into account and not the Parity bit.

M bit

PCE bit

SCI frame

| SB | 8 bit data | STB |

| SB | 7-bit data | PB | STB |

| SB | 9-bit data | STB |

| SB | 8-bit data PB | STB |

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