DSP56366 Technical Data, Rev. 3.1
3-18
Freescale Semiconductor
150
CAS assertion to data not valid (write)
tDH
0.75
× T
C 4.0
33.5
—
21.0
—
ns
151
WR assertion to CAS assertion
tWCS
TC 4.3
45.7
—
29.0
—
ns
152
Last RD assertion to RAS deassertion
tROH
1.5
× T
C 4.0
71.0
—
46.0
—
ns
153
RD assertion to data valid
tGA
TC 7.5
—
42.5
—
25.8
ns
154
RD deassertion to data not valid6
tGZ
0.0
—
0.0
—
ns
155
WR assertion to data active
0.75
× T
C 0.3
37.2
—
24.7
—
ns
156
WR deassertion to data high impedance
0.25
× T
C
—
12.5
—
8.3
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 All the timings are calculated for the worst case. Some of the timings are better for specific cases (e.g., t
PC equals 2 × TC for
read-after-read or write-after-write sequences).
4 Reduced DSP clock speed allows use of Page Mode DRAM with one Wait state (See
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 tGZ.
Table 3-10
DRAM Page Mode Timings, Two Wait States1, 2, 3, 4
No.
Characteristics
Symbol
Expression5
66 MHz
80 MHz
Unit
Min
Max
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
tPC
2
× T
C
1.25
× T
C
45.4
41.1
—
37.5
34.4
—
ns
132
CAS assertion to data valid (read)
tCAC
1.5
× T
C 7.5
1.5
× T
C 6.5
—
15.2
—
12.3
ns
133
Column address valid to data valid (read)
tAA
2.5
× T
C 7.5
2.5
× T
C 6.5
—
30.4
—
24.8
ns
134
CAS deassertion to data not valid (read hold
time)
tOFF
0.0
—
0.0
—
ns
135
Last CAS assertion to RAS deassertion
tRSH
1.75
× T
C 4.0
22.5
—
17.9
—
ns
136
Previous CAS deassertion to RAS deassertion
tRHCP
3.25
× T
C 4.0
45.2
—
36.6
—
ns
137
CAS assertion pulse width
tCAS
1.5
× T
C 4.0
18.7
—
14.8
—
ns
Table 3-9 DRAM Page Mode Timings, One Wait State (Low-Power Applications)1, 2, 3 (continued)
No.
Characteristics
Symbol
Expression
20 MHz4
30 MHz4
Unit
Min
Max
Min
Max