671
SAM4CP [DATASHEET]
43051E–ATPL–08/14
CSAAT: Chip Select Active After Transfer
0 = The Peripheral Chip Select Line rises as soon as the last transfer is achieved.
1 = The Peripheral Chip Select does not rise after the last transfer is achieved. It remains active until a new transfer is requested
on a different chip select.
BITS: Bits Per Transfer
(See the note
(1)
below the register table;
Section 33.8.9 “SPI Chip Select Register” on page 670
).
The BITS field determines the number of data bits transferred. Reserved values should not be used.
SCBR: Serial Clock Baud Rate
In Master Mode, the SPI Interface uses a modulus counter to derive the SPCK baud rate from the Peripheral Clock. The Baud
rate is selected by writing a value from 1 to 255 in the SCBR field. The following equations determine the SPCK baud rate:
Do not program the SCBR field to 0. Triggering a transfer while SCBR is at 0 can lead to unpredictable results.
At reset, SCBR is 0 and the user has to program it at a valid value before performing the first transfer.
Note:
If one of the SCBR fields inSPI_CSRx is set to 1, the other SCBR fields in SPI_CSRx must be set to 1 as well, if they
are required to process transfers. If they are not used to transfer data, they can be set at any value.
DLYBS: Delay Before SPCK
This field defines the delay from NPCS falling edge (activation) to the first valid SPCK transition.
When DLYBS equals zero, the delay is half the SPCK clock period.
Otherwise, the following equations determine the delay:
Value
Name
Description
0
8_BIT
8 bits for transfer
1
9_BIT
9 bits for transfer
2
10_BIT
10 bits for transfer
3
11_BIT
11 bits for transfer
4
12_BIT
12 bits for transfer
5
13_BIT
13 bits for transfer
6
14_BIT
14 bits for transfer
7
15_BIT
15 bits for transfer
8
16_BIT
16 bits for transfer
9
–
Reserved
10
–
Reserved
11
–
Reserved
12
–
Reserved
13
–
Reserved
14
–
Reserved
15
–
Reserved
SPCK Baud rate
SCBR
------------------------------------------------
=
Delay Before SPCK
fperipheralclock
------------DLYBS
=