216
32059L–AVR32–01/2012
AT32UC3B
18.8.9
Chip Select Register n
Name:
CSRn
Access Type:
Read/Write
Offset:
0x30 +0x04*n
Reset Value:
0x00000000
DLYBCT: Delay Between Consecutive Transfers
This field defines the delay between two consecutive transfers with the same peripheral without removing the chip select. The
delay is always inserted after each transfer and before removing the chip select if needed.
When DLYBCT equals zero, no delay between consecutive transfers is inserted and the clock keeps its duty cycle over the
character transfers.
Otherwise, the following equation determines the delay:
DLYBS: Delay Before SPCK
This field defines the delay from NPCS valid to the first valid SPCK transition.
When DLYBS equals zero, the NPCS valid to SPCK transition is 1/2 the SPCK clock period.
Otherwise, the following equations determine the delay:
I
ISCBR: Serial Clock Baud Rate
In Master Mode, the SPI Interface uses a modulus counter to derive the SPCK baud rate from the CLK_SPI. 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:
Writing 0 to the SCBR field is forbidden. Triggering a transfer while SCBR is 0 can lead to unpredictable results.
At reset, SCBR is 0 and the user has to write it at a valid value before performing the first transfer.
IIf a clock divider (SCBRn) is set to 1 and the other SCBR differ from 1, access on CSn is correct but no correct access will be
possible on others CS.
31
30
29
28
27
26
25
24
DLYBCT
23
22
21
20
19
18
17
16
DLYBS
15
14
13
12
11
10
9
8
SCBR
76
543210
BITS
CSAAT
CSNAAT
NCPHA
CPOL
Delay Between Consecutive Transfers
32 DLYBCT
×
CLKSPI
------------------------------------
=
Delay Before SPCK
DLYBS
CLKSPI
---------------------
=
SPCK Baudrate
CLKSPI
SCBR
---------------------
=