ST7263BEx datasheet(86/186 Pages) STMICROELECTRONICS

86 / 186 page

On-chip peripherals

ST7263Bxx

86/186

Doc ID 7516 Rev 8

Baud rate generation

The baud rate for the receiver and transmitter (Rx and Tx) are set independently and

calculated as follows:

with:

PR = 1, 3, 4 or 13 (see SCP[1:0] bits)

TR = 1, 2, 4, 8, 16, 32, 64,128

(see SCT[2:0] bits)

RR = 1, 2, 4, 8, 16, 32, 64,128

(see SCR[2:0] bits)

All these bits are in the SCIBRR register.

Example: If fCPU is 8 MHz (normal mode) and if PR=13 and TR=RR=1, the transmit and

receive baud rates are 38400 baud.

Note:

The baud rate registers MUST NOT be changed while the transmitter or the receiver is

enabled.

Receiver muting and Wakeup 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 can not 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.

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.

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 a 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.

Tx =

(16*PR)*TR

fCPU

Rx =

(16*PR)*RR

fCPU

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