•
Interrupt Flag Clear and Status register (INTFLAG)
•
Status register (STATUS)
•
Data register (DATA)
Optional PAC Write-Protection is denoted by the "PAC Write-Protection" property in each individual
register description.
Write-protection does not apply to accesses through an external debugger.
Related Links
PAC - Peripheral Access Controller
on page 50
32.5.9. Analog Connections
Not applicable.
32.6. Functional Description
32.6.1. Principle of Operation
The USART uses the following lines for data transfer:
•
RxD for receiving
•
TxD for transmitting
•
XCK for the transmission clock in synchronous operation
USART data transfer is frame based. A serial frame consists of:
•
1 start bit
•
From 5 to 9 data bits (MSB or LSB first)
•
No, even or odd parity bit
•
1 or 2 stop bits
A frame starts with the start bit followed by one character of data bits. If enabled, the parity bit is inserted
after the data bits and before the first stop bit. After the stop bit(s) of a frame, either the next frame can
follow immediately, or the communication line can return to the idle (high) state. The figure below
illustrates the possible frame formats. Brackets denote optional bits.
Figure 32-2. Frame Formats
Frame
(IDLE)
St
0
1
2
3
4
[5]
[6]
[7]
[8]
[P]
Sp1
[Sp2]
[St/IDL]
St
Start bit. Signal is always low.
n, [n]
Data bits. 0 to [5..9]
[P]
Parity bit. Either odd or even.
Sp, [Sp]
Stop bit. Signal is always high.
IDLE
No frame is transferred on the communication line. Signal is always high in this state.
Atmel SAM L22G / L22J / L22N [DATASHEET]
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