Atmel SAM4S-EK2 Atmel ATSAM4S-EK2 ATSAM4S-EK2 Data Sheet
Product codes
ATSAM4S-EK2
733
SAM4S [DATASHEET]
11100E–ATARM–24-Jul-13
• CHMODE: Channel Mode
• CPOL: SPI Clock Polarity
– Applicable if USART operates in SPI Mode (Slave or Master, USART_MODE = 0xE or 0xF):
CPOL = 0: The inactive state value of SPCK is logic level zero.
CPOL = 1: The inactive state value of SPCK is logic level one.
CPOL is used to determine the inactive state value of the serial clock (SPCK). It is used with CPHA to produce the required
clock/data relationship between master and slave devices.
clock/data relationship between master and slave devices.
• WRDBT: Wait Read Data Before Transfer
0: The character transmission starts as soon as a character is written into US_THR register (assuming TXRDY was set).
1: The character transmission starts when a character is written and only if RXRDY flag is cleared (Receiver Holding Register has
been read).
been read).
Value
Name
Description
0
NORMAL
Normal Mode
1
AUTOMATIC
Automatic Echo. Receiver input is connected to the TXD pin.
2
LOCAL_LOOPBACK
Local Loopback. Transmitter output is connected to the Receiver Input.
3
REMOTE_LOOPBACK
Remote Loopback. RXD pin is internally connected to the TXD pin.