ppc440epx Applied Micro Circuits Corporation (AMCC), ppc440epx Datasheet - Page 88

• Manufacturer Part Number: ppc440epx
• Description: Powerpc 440epx Embedded Processor
• Manufacturer: Applied Micro Circuits Corporation (AMCC)

440EPx – PPC440EPx Embedded Processor
Table 25. I/O Timing—DDR SDRAM T
Notes:
1. Clock speed is 166MHz. T
2. The timing in this table assumes a single registered DIMM load on the outputs. To adjust the timing for unbuffered DIMMs,
3. To obtain adjusted T
4. To obtain adjusted T
Table 26. I/O Timing—DDR SDRAM T
Notes:
1. T
2. Clock speed for the values in the table is 166MHz.
3. The time values in the table include 1/4 of a cycle at 166MHz (6ns x 0.25 = 1.5 ns).
4. To obtain adjusted T
DDR SDRAM Read Operation
The read data capture logic is responsible for capturing the data outputs from the SDRAM devices and passing the
data back to the system clock domain. The data strobe signal (DQS) signals used to capture data are delayed to
ensure that the rising and falling edges of these strobes are in the middle of the valid window of data.
DDR devices send a DQS coincident with the read data so that the data can be reliably captured by the
PPC440EPx. The edges of these strobe signals are aligned with the data output by the SDRAM devices.
In order to reliably latch the data into a synchronizing FIFO, the PPC440EPx produces an internal, delayed version
of DQS. The amount of delay is user programmable. In the example shown in Figure 12, the delay is set to
approximately 25% of the system clock. A delay compensation circuit in the PPC440EPx keeps this delay
88
MemAddr00:13
BA0:2
BankSel0:1
ClkEn
CAS
RAS
WE
MemData00:07, DM0
MemData08:15, DM1
MemData16:23, DM2
MemData24:31, DM3
MemData32:39, DM4
MemData40:47, DM5
MemData48:55, DM6
MemData56:63, DM7
ECC0:7, DM8
edge.
use the following values by subtracting them from T
18 loads adjust by 2.12ns
T
T
of the cycle time for the lower clock frequency (for example, T
9 loads adjust by 1.12ns
5 loads adjust by 0.41ns
SD
SK
SK
maximum (0.5T
minimum (0.5T
and T
Signal Names
HD
Signal Name
are measured under worst case conditions.
CYC
SA
CYC
HA
SD
values for lower clock frequencies, use 1/2 of the cycle time for the lower clock frequency and subtract
values for lower clock frequencies, use 1/2 of the cycle time for the lower clock frequency and add
and T
+ T
− T
SK
SK
SK
HD
is referenced to MemClkOut falling edge. T
min).
max).
values for lower clock frequencies, subtract 1.5 ns from the values in the table and add 1/4
Reference Signal
SK
SD
DQS0
DQS1
DQS2
DQS3
DQS4
DQS5
DQS6
DQS7
DQS8
, T
and T
SA
Minimum
-0.960
, and T
HD
SA
and adding them to T
HA
T
SK
(ns)
SD
− 1.5 + 0.25T
Maximum
-0.270
SA
T
SD
1.37
1.41
1.40
1.41
1.45
1.40
1.46
1.45
1.46
and T
SK
(ns)
CYC
and T
HA
).
are referenced to MemClkOut rising
Preliminary Data Sheet
HA
Minimum
:
T
Revision 1.29 – July 22, 2008
SA
3.27
(ns)
T
HD
1.23
1.18
1.17
1.20
1.18
1.18
1.17
1.10
1.18
AMCC Proprietary
(ns)
Minimum
T
HA
2.04
(ns)