Samsung S5PC100, User Manual, Page: 392 / 1863

S5PC100 USER’S MANUAL (REV1.0) DRAM CONTROLLER
5.1-9
2.4 PRECHARGE POLICY
There are two ways for the controller to decide precharge policy.
2.4.1 Bank Selective Precharge Policy
Since applications have different page policy preferences, it is hard for the engineer to decide whether to use
open page policy, or close page (auto precharge) policy. Instead of applying the page policy to all of the banks,
the bank selective precharge policy allows the user to choose a precharge policy for each bank Rrefer to
PrechConfig.chip1_policy ). This way, you assign certain applications to a bank that uses an open page policy,
and other applications to a bank that uses a close page (auto precharge) policy.
Open Page Policy: After a READ or WRITE, the accessed row is left open.
Close Page (Auto Precharge) Policy: Right after a READ or WRITE command, the controller issues an auto
precharge to the bank.
2.4.2 Timeout Precharge
If a certain bank uses an open page policy, the row is left open after a data access. If this happens and the bank
that is left open is not scheduled for a specific number of cycles (
PrechConfig.tp_cnt bit-field) the controller
automatically issues a precharge command to close the bank.
T0 T1 T2 T3 T4 T5 T6
CK
DQS
DQ
command
Q0 Q2 Q3
T7
READ
tp_cnt
T8
Q1
Timeout PRE
T0 T1 T2 T3 T4 T5 T6
CK
DQS
DQ
command
Q0 Q2 Q3
T7
WRITE
tp_cnt
T8
Q1
Timeout PRE
BL/2 + 1
t_wr BL/2 + 1
Figure 5.1-4 Timing Diagram of Timeout Precharge