External Memory Expansion Port (Port A)
DSP56367 Technical Data, Rev. 2.1
Freescale Semiconductor
3-17
153
RD assertion to data valid
t
GA
2.5
×
T
C
7.0
—
18.0
ns
154
RD deassertion to data not valid
6
t
GZ
0.0
—
ns
155
WR assertion to data active
0.75
×
T
C
0.3
7.2
—
ns
156
WR deassertion to data high impedance
0.25
×
T
C
—
2.5
ns
1
The number of wait states for Page mode access is specified in the DCR.
2
The refresh period is specified in the DCR.
3
The asynchronous delays specified in the expressions are valid for DSP56367.
4
All the timings are calculated for the worst case. Some of the timings are better for specific cases (e.g., t
PC
equals 4
×
TC for
read-after-read or write-after-write sequences).
5
BRW[1:0] (DRAM control register bits) defines the number of wait states that should be inserted in each DRAM out-of
page-access.
6
RD deassertion will always occur after CAS deassertion; therefore, the restricted timing is t
OFF
and not t
GZ
.
Table 3-10 DRAM Page Mode Timings, Four Wait States
1, 2, 3
No.
Characteristics
Symbol
Expression
4
100 MHz
Unit
Min
Max
131
Page mode cycle time for two consecutive accesses of the
same direction
Page mode cycle time for mixed (read and write) accesses
t
PC
5
×
T
C
4.5
×
T
C
50.0
45.0
—
—
ns
132
CAS assertion to data valid (read)
t
CAC
2.75
×
T
C
5.7
—
21.8
ns
133
Column address valid to data valid (read)
t
AA
3.75
×
T
C
5.7
—
31.8
ns
134
CAS deassertion to data not valid (read hold time)
t
OFF
0.0
—
ns
135
Last CAS assertion to RAS deassertion
t
RSH
3.5
×
T
C
4.0
31.0
—
ns
136
Previous CAS deassertion to RAS deassertion
t
RHCP
6
×
T
C
4.0
56.0
—
ns
137
CAS assertion pulse width
t
CAS
2.5
×
T
C
4.0
21.0
—
ns
138
Last CAS deassertion to RAS assertion
5
BRW[1–0] = 00, 01—Not applicable
BRW[1–0] = 10
BRW[1–0] = 11
t
CRP
—
5.25
×
T
C
6.0
7.25
×
T
C
6.0
—
46.5
66.5
—
—
—
—
ns
ns
139
CAS deassertion pulse width
t
CP
2
×
T
C
4.0
16.0
—
ns
140
Column address valid to CAS assertion
t
ASC
T
C
4.0
6.0
—
ns
Table 3-9 DRAM Page Mode Timings, Three Wait States
1, 2, 3 (continued)
No.
Characteristics
Symbol
Expression
4
100 MHz
Unit
Min
Max