Atmel SAM4S Series, Preliminary Data Sheet

Page: 778 / 1163

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11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
34.8.4 USART Mode Register (SPI_MODE)
Name: US_MR (SPI_MODE)
Address: 0x40024004 (0), 0x40028004 (1)
Access: Read-write
This configuration is relevant only if USART_MODE=0xE or 0xF in “USART Mode Register” on page 774 .
This register can only be written if the WPEN bit is cleared in “USART Write Protect Mode Register” on page 803 .
• USART_MODE: USART Mode of Operation
• USCLKS: Clock Selection
• CHRL: Character Length.
• CPHA: SPI Clock Phase
– Applicable if USART operates in SPI Mode (USART_MODE = 0xE or 0xF):
CPHA = 0: Data is changed on the leading edge of SPCK and captured on the following edge of SPCK.
CPHA = 1: Data is captured on the leading edge of SPCK and changed on the following edge of SPCK.
CPHA determines which edge of SPCK causes data to change and which edge causes data to be captured. CPHA is used
with CPOL to produce the required clock/data relationship between master and slave devices.
31 30 29 28 27 26 25 24
– – – – – – – –
23 22 21 20 19 18 17 16
– – – WRDBT – CPOL
15 14 13 12 11 10 9 8
– – – – – – – CPHA
7 6 5 4 3 2 1 0
CHRL USCLKS USART_MODE
Value Name Description
0xE SPI_MASTER SPI Master
0xF SPI_SLAVE SPI Slave
Value Name Description
0 MCK Master Clock MCK is selected
1 DIV Internal Clock Divided MCK/DIV (DIV=8) is selected
3 SCK Serial Clock SLK is selected
Value Name Description
3 8_BIT Character length is 8 bits