12. DDR2-SDRAM Interface (DBSC2)

Rev.1.00 Jan. 10, 2008 Page 540 of 1658

REJ09B0261-0100

MCK0,
MCK1
MA[14:11]
MA[9:0]
MBA[2:0]
MCKE
MCS
MRAS
MCAS
MWE
MA[10]
ACT
bank A
READ
bank A
Invalid
Invalid
Invalid
Invalid
MDQS[3:0]
MDQ[31:0]
MDM[3:0] Invalid
Invalid Invalid
Invalid
PALL
Invalid
Invalid
REF
SDRAM
command
tRAS
= 9 cycles
Read data
tRC
= 12 cycles
tRP
= 3 cycles
Example of CL = 3
Valid
Valid
Valid
Valid
Valid
Valid
High level
Figure 12.17 tRC Figure 12.17 shows an example of performing auto-refresh after read access of bank A, the page for which had been closed. After issuing an ACT command and READ command for bank A and performing data reading, a PALL command must be used to close all banks in order to perform auto-refresh. In order to issue the PALL command, the tRAS time constraint must be satisfied, and issuing of the PALL command is delayed until this time. Then, when issuing the REF command, both of time constraints tRP and tRC must be satisfied simultaneously. When these constraints are both satisfied, the REF command is issued and auto-refresh is performed.