ST92150CR1TC View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST92150CR1TC

8/16-BIT SINGLE VOLTAGE FLASH MCU FAMILY WITH RAM, E³ ™ (EMULATED EEPROM), CAN 2.0B AND J1850 BLPD

STMicroelectronics 

ASYNCHRONOUS SERIAL COMMUNICATIONS INTERFACE (SCI-A)

ASYNCHRONOUS SERIAL COMMUNICATIONS INTERFACE (Cont’d)

10.6.4.4 Conventional Baud Rate Generation

10.6.4.6 Receiver Muting and Wake-up Feature

The baud rate for the receiver and transmitter (Rx

and Tx) are set independently and calculated as

follows:

Tx = fCPU

(16*PR)*TR

fCPU

Rx =

(16*PR)*RR

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)

In multiprocessor configurations it is often desira-

ble 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 interrupt are inhibited.

A muted receiver may be awakened by one of the

following two ways:

All this bits are in the SCIBRR register.

– by Idle Line detection if the WAKE bit is reset,

Example: If fCPU is 24 MHz and if PR=13 and

TR=RR=2, the transmit and receive baud rates are

57700 baud.

Note: The baud rate registers MUST NOT be

changed while the transmitter or the receiver is en-

abled.

10.6.4.5 Extended Baud Rate Generation

The extended prescaler option gives a very fine

tuning on the baud rate, using a 255 value prescal-

er, whereas the conventional Baud Rate Genera-

tor retains industry standard software compatibili-

ty.

– by Address Mark detection if the WAKE bit is set.

Receiver wakes-up by Idle Line detection when

the Receive line has recognised 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 ad-

dress. 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.

The extended Baud Rate Generator block diagram

is described in the Figure 119.

M Bit PCE Bit

SCI Frame

The output clock rate sent to the transmitter or to

the receiver will be the output from the 16 divider

divided by a factor ranging from 1 to 255 set in the

SCIERPR or the SCIETPR register.

Note: The extended prescaler is activated by set-

ting the SCIETPR or SCIERPR register to a value

other than zero. The baud rates are calculated as

follows:

Tx =

fCPU

Rx =

fCPU

16*ETPR*(PR*TR)

16*ERPR*(PR*TR)

with:

0

0

| SB | 8 bit data | STB |

0

1

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

1

0

| SB | 9-bit data | STB |

1

1

| SB | 8-bit data PB | STB |

SB : Start Bit

STB : Stop Bit

PB : Parity Bit

Note: In case of wake up by an address mark, the

MSB bit of the data is taken into account and not

the parity bit

ETPR = 1,..,255 (see SCIETPR register)

ERPR = 1,.. 255 (see SCIERPR register)

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