4 spi transmit data register – Rainbow Electronics AT91CAP9S250A User Manual

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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).

–

LASTXFER

–

PCS