r8a77850anbg Renesas Electronics Corporation., r8a77850anbg Datasheet - Page 570

• Manufacturer Part Number: r8a77850anbg
• Description: Renesas 32-bit Risc Microcomputer Superh? Risc Engine Family
• Manufacturer: Renesas Electronics Corporation.

12. DDR2-SDRAM Interface (DBSC2)
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.
Rev.1.00 Jan. 10, 2008 Page 540 of 1658
REJ09B0261-0100
Example of CL = 3
MCK0,
MCK1
MCKE
MCS
MRAS
MCAS
MWE
MA[14:11]
MA[9:0]
MA[10]
MBA[2:0]
MDQS[3:0]
MDM[3:0]
MDQ[31:0]
SDRAM
command
bank A
ACT
Valid
Valid
Valid
Invalid
Invalid
Invalid
High level
READ
bank A
Valid
Valid
Valid
Invalid
Figure 12.17 tRC
tRAS
= 9 cycles
tRC
= 12 cycles
Invalid
Invalid
Read data
Invalid
Invalid
PALL
tRP
= 3 cycles
Invalid
Invalid
REF