41594B datasheet(288/372 Pages) MICROCHIP

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PIC12LF1840T48A

DS41594B-page 288

Preliminary

 2011-2012 Microchip Technology Inc.

26.4.2

SYNCHRONOUS SLAVE MODE

The following bits are used to configure the EUSART

for Synchronous slave operation:

• SYNC = 1

• CSRC = 0

• SREN = 0 (for transmit); SREN = 1 (for receive)

• CREN = 0 (for transmit); CREN = 1 (for receive)

• SPEN = 1

Setting the SYNC bit of the TXSTA register configures the

device for synchronous operation. Clearing the CSRC bit

of the TXSTA register configures the device as a slave.

Clearing the SREN and CREN bits of the RCSTA register

ensures that the device is in the Transmit mode,

otherwise the device will be configured to receive. Setting

the SPEN bit of the RCSTA register enables the

EUSART.

26.4.2.1

EUSART Synchronous Slave

Transmit

The operation of the Synchronous Master and Slave

modes

are

identical

(see

Section 26.4.1.3

“Synchronous Master Transmission”), except in the

case of the Sleep mode.

If two words are written to the TXREG and then the

SLEEP instruction is executed, the following will occur:

The first character will immediately transfer to

the TSR register and transmit.

The second word will remain in the TXREG reg-

ister.

The TXIF bit will not be set.

After the first character has been shifted out of

TSR, the TXREG register will transfer the second

character to the TSR and the TXIF bit will now be

set.

If the PEIE and TXIE bits are set, the interrupt

will wake the device from Sleep and execute the

next instruction. If the GIE bit is also set, the

program will call the Interrupt Service Routine.

26.4.2.2

Synchronous Slave Transmission

Set-up:

Set the SYNC and SPEN bits and clear the

CSRC bit.

Clear the ANSEL bit for the CK pin (if applicable).

Clear the CREN and SREN bits.

If interrupts are desired, set the TXIE bit of the

PIE1 register and the GIE and PEIE bits of the

INTCON register.

If 9-bit transmission is desired, set the TX9 bit.

Enable transmission by setting the TXEN bit.

If 9-bit transmission is selected, insert the Most

Significant bit into the TX9D bit.

Start transmission by writing the

Least

Significant 8 bits to the TXREG register.

TABLE 26-9:

SUMMARY OF REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE

TRANSMISSION

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

on Page

BAUDCON

ABDOVF

RCIDL

—SCKP

BRG16

—

WUE

ABDEN

274

INTCON

GIE

PEIE

TMR0IE

INTE

IOCIE

TMR0IF

INTF

IOCIF

PIE1

TMR1GIE

ADIE

RCIE

TXIE

SSP1IE

CCP1IE

TMR2IE

TMR1IE

PIR1

TMR1GIF

ADIF

RCIF

TXIF

SSP1IF

CCP1IF

TMR2IF

TMR1IF

RCSTA

SPEN

RX9

SREN

CREN

ADDEN

FERR

OERR

RX9D

273

TXREG

EUSART Transmit Data Register

265*

TXSTA

CSRC

TX9

TXEN

SYNC

SENDB

BRGH

TRMT

TX9D

272

Legend: — = unimplemented location, read as ‘0’. Shaded cells are not used for synchronous slave transmission.

* Page provides register information.

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