4 spi transmit data register – Rainbow Electronics AT91CAP9S250A User Manual
Page 475
475
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
33.7.4
SPI Transmit Data Register
Name: SPI_TDR
Access Type: Write-only
• TD: Transmit Data
Data to be transmitted by the SPI Interface is stored in this register. Information to be transmitted must be written to the
transmit data register in a right-justified format.
PCS: Peripheral Chip Select
This field is only used if Variable Peripheral Select is active (PS = 1).
If PCSDEC = 0:
PCS = xxx0
NPCS[3:0] = 1110
PCS = xx01
NPCS[3:0] = 1101
PCS = x011
NPCS[3:0] = 1011
PCS = 0111
NPCS[3:0] = 0111
PCS = 1111
forbidden (no peripheral is selected)
(x = don’t care)
If PCSDEC = 1:
NPCS[3:0] output signals = PCS
• LASTXFER: Last Transfer
0 = No effect.
1 = The current NPCS is deasserted after the character written in TD has been transferred. When CSAAT is set, this allows
to close the communication with the current serial peripheral by raising the corresponding NPCS line as soon as TD trans-
fer has completed.
This field is only used if Variable Peripheral Select is active (PS = 1).
31
30
29
28
27
26
25
24
–
–
–
–
–
–
–
LASTXFER
23
22
21
20
19
18
17
16
–
–
–
–
PCS
15
14
13
12
11
10
9
8
TD
7
6
5
4
3
2
1
0
TD