![Intel IXP45X Developer'S Manual Download Page 606](http://html1.mh-extra.com/html/intel/ixp45x/ixp45x_developers-manual_2073092606.webp)
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Memory Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
606
Order Number: 306262-004US
11.2.2.10 DDRI SDRAM Read Cycle
The MCU performance is optimized for page hits and the MCUs behavior is different for
the hit and miss scenario.
The waveform for a read including the row activation in the case of a page miss is
illustrated in
. For a page hit, the two cycles required for row activation are
saved resulting in lower first word read latency.
The MCU supports optimized performance for random address transactions. This
optimization eliminates the need of the DDRI SDRAM Control Block to issue the
transaction command to the DDRI array if the previous transaction is the same type
(read or write). In addition, the DDRI SDRAM Control Block supports pipelining of
transactions which allows the column address of the next transaction to be issued
before the current transaction’s data transfer is completed by the DDRI SDRAM
devices. These optimizations are illustrated in
for random read memory
transactions.
Figure 113. DDRI SDRAM Pipelined Reads
B0406-02
Command
CK_N
CK
Read
Read
Read
Read
NOP
NOP
Address
Bank Col n
Bank Col x
Bank Col b
Bank Col g
CL = 2
DQS
DQ
Do n
Do n'
Do x
Do x'
Do b
Do b'
Do g