Microchip Technology MA330031-2 Data Sheet

DS70000657H-page 282

 2011-2013 Microchip Technology Inc.

1.

In multi-node, direct-connect UART networks,
UART receive inputs react to the
complementary 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 ini-
tialized, 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.
a)

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

b)

If URXINV = 1, use a pull-down resistor on
the RX pin. 

2.

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.

Many useful resources are provided on the main prod-
uct page of the Microchip web site for the devices listed
in this data sheet. This product page, which can be
accessed using this 

, contains the latest updates

and additional information.

20.2.1

KEY RESOURCES

• “UART” (DS70582) in the “dsPIC33/PIC24 

• Code Samples
• Application Notes
• Software Libraries
• Webinars
• All Related “dsPIC33/PIC24 Family Reference 

 Sections

• Development Tools

In the event you are not able to access the
product page using the link above, enter
this URL in your browser: