DSPIC33EP128GS708 datasheet(258/484 Pages) MICROCHIP

258 / 484 page

dsPIC33EPXXXGS70X/80X FAMILY

DS70005258C-page 258

 2016-2018 Microchip Technology Inc.

20.1

UART Helpful Tips

In multi-node, direct connect UART networks,

UART receive inputs react to the complemen-

tary logic level defined by the URXINV bit

(UxMODE<4>), which defines the Idle state, the

default of which is logic high (i.e., URXINV = 0).

Because remote devices do not initialize at the

same time, it is likely that one of the devices,

because the RX line is floating, will trigger a Start

bit detection and will cause the first byte received,

after the device has been initialized, to be invalid.

To avoid this situation, the user should use a pull-

up or pull-down resistor on the RX pin depending

on the value of the URXINV bit.

If URXINV = 0, use a pull-up resistor on the

UxRX pin.

If URXINV = 1, use a pull-down resistor on

the UxRX pin.

The first character received on a wake-up from

Sleep mode, caused by activity on the UxRX pin

of the UARTx module, will be invalid. In Sleep

mode, peripheral clocks are disabled. By the

time the oscillator system has restarted and

stabilized from Sleep mode, the baud rate bit

sampling clock, relative to the incoming UxRX

bit timing, is no longer synchronized, resulting in

the first character being invalid; this is to be

expected.

20.2

UART Resources

Many useful resources are provided on the main prod-

uct page of the Microchip website for the devices listed

in this data sheet. This product page contains the latest

updates and additional information.

20.2.1

KEY RESOURCES

• “Universal Asynchronous Receiver

Transmitter (UART)” (DS70000582) in the

“dsPIC33/PIC24 Family Reference Manual”

• Code Samples

• Application Notes

• Software Libraries

• Webinars

• All Related “dsPIC33/PIC24 Family Reference

Manual” Sections

• Development Tools

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