Datasheet

dsPIC33FJ16(GP/MC)101/102 AND dsPIC33FJ32(GP/MC)101/102/104
DS70652E-page 210  2011-2012 Microchip Technology Inc.
18.1 UART Helpful Tips
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 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.
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 UART 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.
18.2 UART Resources
Many useful resources are provided on the main
product page of the Microchip web site for the devices
listed in this data sheet. This product page, which can
be accessed using this link, contains the latest updates
and additional information.
18.2.1 KEY RESOURCES
• Section 17. “UART” (DS70188) in the
“dsPIC33F/PIC24H Family Reference Manual”
• Code Samples
• Application Notes
• Software Libraries
• Webinars
• All related “dsPIC33F/PIC24H Family Reference
Manual” sections
• Development Tools
Note: In the event you are not able to access
the product page using the link above,
enter this URL in your browser:
http://www.microchip.com/wwwproducts/
Devices.aspx?dDocName=en554109