MB81ES653225-12/-12L
17
Row/column address allocation at each page length is shown as the following table. For example, A
14
(row
address) at 32 page length mode is corresponded to A
5
(column address) at 64 page length mode.
14. PRECHARGE AND PRECHARGE OPTION (PRE, PALL)
SDR I/F FCRAM memory core is the same as conventional DRAMs’, requiring precharge and refresh operations.
Precharge rewrites the bit line and to reset the internal Row address line and is executed by the Precharge
command (PRE) . With the Precharge command, SDR I/F FCRAM will automatically be in standby state after
precharge time (t
RP
) . The precharged bank is selected by combination of AP and BA
when Precharge command
is asserted. If AP
=
High, all banks are precharged regardless of BA (PALL) . If AP
=
Low, a bank to be selected
by BA is precharged (PRE) . The auto-precharge enters precharge mode at the end of burst mode of read or
write without Precharge command assertion. This auto precharge is entered by AP
=
High when a read or write
command is asserted. Refer to “1. COMMAND TRUTH TABLE” in section “
■
FUNCTIONAL TRUTH TABLE”.
15. AUTO-REFRESH (REF)
Auto-refresh uses the internal refresh address counter. The SDR I/F FCRAM Auto-refresh command (REF)
generates Precharge command internally. All banks of SDR I/F FCRAM should be precharged prior to the Auto-
refresh command. The Auto-refresh command should also be asserted every 3.9
μ
s or a total 8192 refresh
commands within 32 ms period.
16. SELF-REFRESH ENTRY (SELF)
Self-refresh function provides automatic refresh by an internal timer as well as Auto-refresh and will continue
the refresh function until cancelled by SELFX. The Self-refresh is entered by applying an Auto-refresh command
in conjunction with CKE
=
Low (SELF) . Once SDR I/F FCRAM enters the self-refresh mode, all inputs except
for CKE will be “don’t care” (either logic high or low level state) and outputs will be in a High-Z state. During a
self-refresh mode, CKE
=
Low should be maintained. SELF command should only be issued after last read data
has been appeared on DQ
Note : When the burst refresh method is used, a total of 8,192 auto-refresh commands within 2 ms must be asserted
prior to the self-refresh mode entry.
17. SELF-REFRESH EXIT (SELFX)
To exit self-refresh mode, apply minimum t
CKSP
after CKE brought high, and then the No Operation command
(NOP) or the Deselect command (DESL) should be asserted within one t
RC
period. CKE should be held High
within one t
RC
period after t
CKSP
. Refer to “16. SELF-REFRESH ENTRY AND EXIT TIMING” in section “
■
TIMING
DIAGRAMS” for the detail. It is recommended to assert an Auto-refresh command just after the t
RC
period to
avoid the violation of refresh period.
Note : When the burst refresh method is used, a total of 8,192 auto-refresh commands within 2 ms must be asserted
after the self-refresh exit.
32 page
Row : A
14
to A
0
Column : A
4
to A
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
4
3
2
1
0
64 page
Row : A
13
to A
0
Column : A
0
to A
5
0
1
2
3
4
5
6
7
8
9
10
11
12
13
5
4
3
2
1
0
128 page
Row : A
12
to A
0
Column : A
6
to A
0
0
1
2
3
4
5
6
7
8
9
10
11
12
6
5
4
3
2
1
0