Datasheet

z Burst read with auto precharge
If A10 is HIGH when a Read Command is issued, the Read with Auto-Precharge function is engaged. The
DDR2 SDRAM starts an Auto-Precharge operation on the rising edge which is (AL + BL/2) cycles later from the
Read with AP command if t
RAS
(min) and t
RTP
are satisfied. If t
RAS
(min) is not satisfied at the edge, the start point
of Auto-Precharge operation will be delayed until t
RAS
(min) is satisfied. If t
RTP
(min) is not satisfied at the edge,
the start point of Auto-precharge operation will be delayed until t
RTP
(min) is satisfied.
In case the internal precharge is pushed out by t
RTP
, t
RP
starts at the point where the internal precharge
happens (not at the next rising clock edge after this event). So for BL = 4 the minimum time from Read with
Auto-Precharge to the next Activate command becomes AL + t
RTP
+ t
RP
. For BL = 8 the time from Read with
Auto-Precharge to the next Activate command is AL + 2 + t
RTP
+ t
RP
. Note that both parameters t
RTP
and t
RP
have to be rounded up to the next integer value. In any event internal precharge does not start earlier than two
clocks after the last 4-bit prefetch.
A new bank active (command) may be issued to the same bank if the following two conditions are satisfied
simultaneously:
(1) The RAS# precharge time (t
RP
) has been satisfied from the clock at which the Auto-Precharge begins.
(2) The RAS# cycle time (t
RC
) from the previous bank activation has been satisfied.
z Burst write with auto precharge
If A10 is HIGH when a Write Command is issued, the Write with Auto-Precharge function is engaged. The
DDR2 SDRAM automatically begins precharge operation after the completion of the burst write plus Write
recovery time (t
WR
). The bank undergoing auto-precharge from the completion of the write burst may be
reactivated if the following two conditions are satisfied.
(1) The data-in to bank activate delay time (WR + t
RP
) has been satisfied.
(2) The RAS# cycle time (t
RC
) from the previous bank activation has been satisfied.
Table 14.Precharge & Auto Precharge Clariification
From Command To Command
Minimum Delay between “From
Command” to “To Command”
Unit Notes
Read
Precharge (to same Bank as Read) AL+BL/2+max(RTP,2)-2
t
CK
1,2
Precharge All AL+BL/2+max(RTP,2)-2
Read w/AP
Precharge (to same Bank as Read w/AP) AL+BL/2+max(RTP,2)-2 t
CK
1,2
Precharge All AL+BL/2+max(RTP,2)-2
Write
Precharge (to same Bank as Write) WL+BL/2+t
WR
t
CK
2
Precharge All WL+BL/2+t
WR
Write w/AP
Precharge (to same Bank as Write w/AP) WL+BL/2+t
WR
t
CK
2
Precharge All WL+BL/2+t
WR
Precharge
Precharge (to same Bank as Precharge) 1 t
CK
2
Precharge All 1
Precharge All
Precharge 1 t
CK
2
Precharge All 1
NOTE 1: RTP [cycles] =RU {t
RTP
[ns]/t
CK
(avg) [ns]}, where RU stands for round up.
NOTE 2: For a given bank, the precharge period should be counted from the latest precharge command, either
one bank precharge or precharge all, issued to that bank.The prechrage period is satisfied after t
RP
or t
RP
all(=t
RP
for 4 bank device) depending on the latest precharge command issued to that bank.
AS4C32M16D2A-25BIN
Alliance Memory Inc.
511 Taylor Way, San Carlos, CA 94070 TEL: [phone] FAX: [phone]
Alliance Memory Inc. reserves the right to change products or specification without notice
Rev.1.2
19
Jun./2014