Samsung S5PC100 User Manual page 392

S5PC100 USER'S MANUAL (REV1.0)
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
CK
command
READ
DQS
DQ
T0
CK
command WRITE
DQS
DQ
BL/2 + 1
T1 T2 T3
BL/2 + 1
T1 T2 T3
Q0 Q1 Q2
Figure 5.1-4 Timing Diagram of Timeout Precharge
tp_cnt
T4 T5
Q0 Q1 Q2
t_wr
T4 T5
Q3
DRAM CONTROLLER
T6 T7
Timeout PRE
Q3
tp_cnt
T6 T7
Timeout PRE
T8
T8
5.1-9