![](http://datasheet.mmic.net.cn/330000/MB814100A-60_datasheet_16435836/MB814100A-60_20.png)
20
MB814100A-60/MB814100A-70/MB814100A-80
t
RSC
t
OH
HIGH-Z
VALID DATA
t
CWL
t
RWL
t
WP
COLUMN ADDRESS
Parameter
Unit
Min.
—
Max.
Min.
—
Max.
60
ns
No.
Min.
—
Max.
50
55
MB814100A-70
MB814100A-80
MB814100A-60
(At recommended operating conditions unless otherwise noted.)
Fig. 15 - CAS-BEFORE-RAS REFRESH COUNTER TEST CYCLE
Symbol
30
35
—
—
ns
—
30
VALID DATA
Column Address Hold
92
CAS to WE Delay
93
94
CAS Puls width
RAS Hold Time
55
60
—
—
ns
—
50
55
60
—
—
ns
—
50
55
60
—
—
ns
—
50
DESCRIPTION
A special timing sequence using the CAS-before-RAS refresh counter test cycle provides a convenient method to verify the functionality
of CAS-before-RAS refresh circuitry. If, after a CAS-before-RAS refresh cycle. CAS makes a transition from High to Low while RAS is
held Low, read and write operations are enabled as shown above. Row and column addresses are defined as follows:
Row Address: Bits A
0
through A
10
are defined by the on-chip refresh counter.
Column Address: Bits A
0
through A
10
are defined by latching levels on A
0
-A
9
at the second falling edge of CAS.
The CAS-before-RAS Counter Test procedure is as follows ;
1) Initialize the internal refresh address counter by using 8 RAS only refresh cycles.
2) Use the same column address throughout the test.
3) Write “0” to all 1024 row addresses at the same column address by using normal write cycles.
4) Read “0” written in procedure 3) and check; simultaneously write “1” to the same addresses by using CAS-before-RAS refresh
counter test (read-modify-write cycles). Repeat this procedure 1024 times with addresses generated by the internal refresh
address counter.
5) Read and check data written in procedure 4) by using normal read cycle for all 1024 memory locations.
6) Reverse test data and repeat procedures 3), 4), and 5).
Note:
Assumes that CAS-before-RAS refresh counter test cycle only.
Access Time from CAS
90
90
t
FCAC
t
FCAH
t
FCWD
t
FCAS
t
FRSH
RAS
CAS
A
0
to A
10
V
IH
V
IL
V
IH
V
IL
V
IH
V
IL
WE
(Read)
D
OUT
V
IH
V
IL
V
OH
V
OL
D
IN
V
OH
V
OL
WE
(Write)
V
IH
V
IL
t
RP
t
FRSH
t
CP
t
CHR
t
CSR
t
FCAS
t
RAL
t
FCAH
t
RRH
t
RCH
t
OFF
t
FCAC
t
ASC
t
ON
t
WHR
t
WSR
t
RCS
t
FCWD
t
DS
t
DH
“H” or “L”