PKP
VS1000 P
ROGRAMMER
’
S
G
UIDE
VSMPG
2. Falling edge xCS mode
3. Rising edge xCS mode
In interrupted xCS mode the clock is only listened to if xCS is active. Reception starts
when xCS state changes from high to low. If xCS is deasserted in the middle of the
transfer, the reception is aborted.
In falling edge xCS mode reception starts when xCS state changes from high to low, but
transfer is not aborted if xCS changes from low to high mid-transfer. If another high to
low transition is encountered during the transfer of SPI_1 bits, the partially
received data is moved to the data register, SPI_ST_BREAK is set, interrupt 0 request
is sent, and a new transfer is initiated.
Rising edge xCS mode works like the falling edge xCS mode, except that the polarity of
the synchronization is reversed.
16.3
Registers
SPI registers, prefix SPIx_
Reg
Type
Reset
Abbrev
Description
0
r/w
0
CONFIG[10:0]
Configuration
1
r/w
0
CLKCONFIG
Clock configuration
2
r/w
0
STATUS[7:0]
Status
3
r/w
0
DATA
Sent / received data
4
r/w
0
FSYNC
SSI Sync data in master mode
5
r/w
0
DEFAULT
Data to send (slave) if SPI_ST_TXFULL=’0’
16.3.1
Main Configuration SPIx_CONFIG
SPIx_CONFIG Bits
Name
Bits
Description
SPI_CF_SRESET
11
SPI software reset
SPI_CF_RXFIFOMODE
10
’0’ = interrupt always when a word is received,
’1’ = Interrupt only when FIFO register full or CS
deasserted with receive register full
SPI_CF_RXFIFO
9
Receive FIFO enable
SPI_CF_TXFIFO
8
Transmit FIFO enable
SPI_CF_XCSMODE
7:6
xCS mode in slave mode
SPI_CF_MASTER
5
Master mode
SPI_CF_DLEN
4:1
Data length in bits
SPI_CF_FSIDLE
0
Frame sync idle state
SPI_CF_XCSMODE selects xCS mode for slave operation. ’00’ is interrupted xCS
mode, ’10’ is falling edge xCS mode, and ’11’ is rising edge xCS mode.
Rev. 0.20
2011-10-04
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