Rainbow Electronics AT91CAP9S250A - Manual (Page 222)

222
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
account this feature of the SDRAM device. In the case of DDR-SDRAM devices, transfers start
at address 0x04/0x08/0x0C. In the case of SDR-SDRAM devices, transfers start at address
0x14/0x18/0x1C. Two read commands are issued to avoid wrapping when the boundary is
reached. The last read command may generate additional reading (1 read cmd = 4 DDR words
or 1 read cmd = 8 SDR words ).
To avoid additional reading, it is possible to use the burst stop command to truncate the read
burst and to decrease power consumption.
Figure 23-8. Single Read Access, Row Close, Latency= 2, DDR-SDRAM Devices
Figure 23-9. Single Read Access, Row Close, Latency= 2, SDR-SDRAM Devices
Trp Trcd Latency =2
SDCLK
Row a Col a
A[12:0]
NOP PRCHG NOP ACT NOP READ BST NOP
COMMAND
0
BA[1:0]
DQS[1]
DQS[0]
Da Db
D[15:0]
3
DM[1:0]
Row a col a
NOP PRCHG NOP ACT NOP READ BST NOP
0
Trp Trcd Latency =2
SDCLK
A[12:0]
COMMAND
BA[1:0]
DaDb
D[31:0]
3
DM[3:0]