Table of Contents
Advertisement
USART Operation: UART Mode
USART Receive Interrupt Operation
The URXIFGx interrupt flag is set each time a character is received and loaded
into UxRXBUF. An interrupt request is generated if URXIEx and GIE are also
set. URXIFGx and URXIEx are reset by a system reset PUC signal or when
SWRST = 1. URXIFGx is automatically reset if the pending interrupt is served
(when URXSE = 0) or when UxRXBUF is read. The operation is shown in
Figure 13−11.
Figure 13−11.Receive Interrupt Operation
SYNC
Valid Start Bit
Receiver Collects Character
URXSE
τ
From URXD
Erroneous Character Rejection
PE
FE
BRK
URXEIE
URXWIE
RXWAKE
Non-Address Character Rejection
URXEIE is used to enable or disable erroneous characters from setting
URXIFGx. When using multiprocessor addressing modes, URXWIE is used
to auto-detect valid address characters and reject unwanted data characters.
Two types of characters do not set URXIFGx:
-
-
When URXEIE = 1 a break condition will set the BRK bit and the URXIFGx flag.
13-18
USART Peripheral Interface, UART Mode
Character Received
or
Break Detected
Erroneous characters when URXEIE = 0
Non-address characters when URXWIE = 1
URXS
S
Clear
URXIEx
S
URXIFGx
Clear
SWRST
PUC
UxRXBUF Read
URXSE
IRQA
Interrupt Service
Requested
Advertisement
Table of Contents
