Rainbow Electronics AT75C220 - Manual (Page 131)

AT75C220
131
SPI Transmit Data Register
Register Name:SP_TDR
Access Type:Write-only
Reset Value:–
• TD: Transmit Data
Data that is 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
31 30 29 28 27 26 25 24
– – – – – – – –
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