7721 Group User’s Manual
17–95
Appendix 11. Electrical characteristics
APPENDIX
DRAM control switching characteristics (VCC = 5 V ± 10 %, VSS = 0 V, Ta = –20 to 85 °C,
f(XIN) = 25 MHz, unless otherwise noted)
Note: The limits depend on f(XIN). Table 5 lists calculation formulas for the limits.
Limits
tw(RASL)
tw(CASL)
tw(RASH)
td(RAS–CAS)
td(RA–RAS)
th(RAS–RA)
td(CA–CAS)
th(CAS–CA)
td(R/W–RAS)
th(CAS–R/W)
td(E–CA)
td(E–RASL)
td(E–CASL)
td(E–RASH)
td(E–CASH)
____
RAS low–level pulse width
____
CAS low–level pulse width
____
CAS high–level pulse width
____
RAS–CAS delay time
____
Row address delay time before RAS
____
Row address hold time after RAS
____
Column address delay time before CAS
____
Column address hold time after CAS
__
____
R/W delay time before RAS
__
____
R/W hold time after CAS
__
Column address delay time after E’s low level
____
__
RAS delay time after E’s low level
____
__
CAS delay time after E’s low level
____
__
RAS delay time after E’s high level
____
__
CAS delay time after E’s high level
Max.
Parameter
Read
Symbol
Unit
ns
Note: Figure 13 shows the test circuit.
Limits
tw(RASL)
tw(CASL)
tw(RASH)
td(RAS–CAS)
td(RA–RAS)
th(RAS–RA)
td(CA–CAS)
th(CAS–CA)
td(R/W–RAS)
th(CAS–R/W)
td(E–RASL)
td(E–CASL)
td(E–RASH)
td(E–CASH)
____
RAS low–level pulse width
____
CAS low–level pulse width
____
CAS high–level pulse width
____
RAS–CAS delay time
____
Row address delay time before RAS
____
Row address hold time after RAS
____
Column address delay time before CAS
____
Column address hold time afrer CAS
__
____
R/W delay time before RAS
__
____
R/W hold time after CAS
____
__
RAS delay time after E’s low level
____
__
CAS delay time after E’s low level
____
__
RAS delay time after E’s high level
____
__
CAS delay time after E’s high level
Max.
Parameter
Write
Symbol
Min.
120
55
60
5
18
10
60
18
80
0
Unit
ns
(Note)
30
115
20
Note: Figure 13 shows the test circuit.
Limits
tw(RASL)
tw(CASL)
td(CAS–RAS)
th(RAS–CAS)
____
RAS low–level pulse width
____
CAS low–level pulse width
____
___
CAS–RAS delay time
____
CAS hold time after RAS
Max.
Parameter
Refresh state
Symbol
Min.
120
55
17.5
Unit
ns
(Note)
Note: Figure 13 shows the test circuit.
65
30
77.5
20
Min.
120
92.5
60
28
5
18
5
100
18
0