PIC16LC63A-04 Datasheet, PDF(67/184 Page) Microchip Technology – 8-Bit CMOS Microcontrollers with A/D Converter

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

PIC16LC63A-04 Datasheet, PDF (67/184 Pages) Microchip Technology – 8-Bit CMOS Microcontrollers with A/D Converter

◁

PIC16C63A/65B/73B/74B

11.1 USART Baud Rate Generator

(BRG)

The BRG supports both the Asynchronous and Syn-

chronous modes of the USART. It is a dedicated 8-bit

baud rate generator. The SPBRG register controls the

period of a free running 8-bit timer. In Asynchronous

mode, bit BRGH (TXSTA<2>) also controls the baud

rate. In Synchronous mode, bit BRGH is ignored.

Table 11-1 shows the formula for computation of the

baud rate for different USART modes, which only apply

in Master mode (internal clock).

Given the desired baud rate and Fosc, the nearest inte-

ger value for the SPBRG register can be calculated

using the formula in Table 11-1. From this, the error in

baud rate can be determined.

It may be advantageous to use the high baud rate

(BRGH = 1) even for slower baud clocks. This is

because the FOSC/(16(X + 1)) equation can reduce the

baud rate error in some cases.

Writing a new value to the SPBRG register causes the

BRG timer to be reset (or cleared). This ensures the

BRG does not wait for a timer overflow before output-

ting the new baud rate.

11.1.1 SAMPLING

The data on the RC7/RX/DT pin is sampled three times

near the center of each bit time by a majority detect cir-

cuit to determine if a high or a low level is present at the

RX pin.

TABLE 11-1:

SYNC

BAUD RATE FORMULA

BRGH = 0 (Low Speed)

(Asynchronous) Baud Rate = FOSC/(64(SPBRG+1))

(Synchronous) Baud Rate = FOSC/(4(SPBRG+1))

BRGH = 1 (High Speed)

Baud Rate = FOSC/(16(SPBRG+1))

N/A

TABLE 11-2: REGISTERS ASSOCIATED WITH BAUD RATE GENERATOR

Address Name

Bit 7

Bit 6 Bit 5

Bit 4 Bit 3 Bit 2

Bit 1 Bit 0

Value on:

POR,

BOR

98h

TXSTA CSRC TX9 TXEN SYNC â BRGH TRMT TX9D

18h

RCSTA SPEN RX9 SREN CREN â FERR OERR RX9D

99h

SPBRG Baud Rate Generator register

Legend: x = unknown, - = unimplemented, read as '0'. Shaded cells are not used by the BRG.

0000 -010

0000 -00x

0000 0000

Value on

all other

RESETS

0000 -010

0000 -00x

0000 0000

DS30605C-page 67

▷