PIC16F84A datasheet(105/337 Pages) MICROCHIP

105 / 337 page

DS30234D-page 105

PIC16C6X

12.0

UNIVERSAL SYNCHRONOUS

ASYNCHRONOUS RECEIVER

TRANSMITTER (USART)

MODULE

The Universal Synchronous Asynchronous Receiver

Transmitter (USART) module is one of the two serial

I/O modules. (USART is also known as a Serial Com-

munications Interface or SCI) The USART can be con-

ﬁgured as a full duplex asynchronous system that can

communicate with peripheral devices such as CRT ter-

Applicable Devices

61 62 62A R62 63 R63 64 64A R64 65 65A R65 66 67

minals and personal computers, or it can be conﬁgured

as a half duplex synchronous system that can commu-

nicate with peripheral devices such as A/D or D/A inte-

grated circuits, Serial EEPROMs etc.

The USART can be conﬁgured in the following modes:

• Asynchronous (full duplex)

• Synchronous - Master (half duplex)

• Synchronous - Slave (half duplex)

Bit SPEN (RCSTA<7>) and bits TRISC<7:6> have to

be set in order to conﬁgure pins RC6/TX/CK and

RC7/RX/DT as the Universal Synchronous Asynchro-

nous Receiver Transmitter.

FIGURE 12-1: TXSTA: TRANSMIT STATUS AND CONTROL REGISTER (ADDRESS 98h)

R/W-0

U-0

R/W-0

R-1

R/W-0

CSRC

TX9

TXEN

SYNC

—

BRGH

TRMT

TX9D

R = Readable bit

W = Writable bit

U = Unimplemented bit,

read as ‘0’

- n =Value at POR reset

bit7

bit0

bit 7:

CSRC: Clock Source Select bit

Asynchronous mode

Don’t care

Synchronous mode

1 = Master mode (Clock generated internally from BRG)

0 = Slave mode (Clock from external source)

bit 6:

TX9: 9-bit Transmit Enable bit

1 = Selects 9-bit transmission

0 = Selects 8-bit transmission

bit 5:

TXEN: Transmit Enable bit

1 = Transmit enabled

0 = Transmit disabled

Note: SREN/CREN overrides TXEN in SYNC mode.

bit 4:

SYNC: USART Mode Select bit

1 = Synchronous mode

0 = Asynchronous mode

bit 3:

Unimplemented: Read as '0'

bit 2:

BRGH: High Baud Rate Select bit

Asynchronous mode

1 = High speed

Note:

For the PIC16C63/R63/65/65A/R65 the asynchronous high speed mode (BRGH = 1) may

experience a high rate of receive errors. It is recommended that BRGH = 0. If you desire a

higher baud rate than BRGH = 0 can support, refer to the device errata for additional infor-

mation or use the PIC16C66/67.

0 = Low speed

Synchronous mode

Unused in this mode

bit 1:

TRMT: Transmit Shift Register Status bit

1 = TSR empty

0 = TSR full

bit 0:

TX9D: 9th bit of transmit data. Can be parity bit.

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