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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262-004US
603
Memory Controller—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
The timing parameters for DDR reads are defined in
. Both Read to Write
(IXP45X/IXP46X network processors t
RTW
) and Read to Command (IXP45X/IXP46X
network processors t
RTCMD
) are defined the same. It is important to note that they
remain separate for two reasons: 1) For similarity to the DDR Write timing parameters,
and 2) to allow for flexibility in programming the MCU that might not have been
comprehended at the time of its design. Both parameters take into account CAS latency
(JEDEC: t
CAS
) and Burst Length (JEDEC: BL).
Note:
Burst Length is fixed at four for the IXP45X/IXP46X network processors.
Note:
The MCU allows for back-to-back reads, so long as they are to a currently open page.
Figure 110. MCU Active, Precharge, Refresh Command Timing Diagram
B4215-001
m_clk
tRC
t
RAS
A
Notes:
t
RC
= Active to Active, Active to Refresh
t
RFC
= Refresh to Active, Refresh to Refresh
t
RP
= Precharge Command Period
t
RAS
= Active to Precharge
t
RCD
= Active to Read, Active to Write
ACT or ARF
t
RFC
ARF
PCH
A/A
A/A
Next command
ACT or ARF
ACT
t
RP
PCH
CMD
t
RCD
R/W
Read or Write
t0
tn
tn+1
tn+2
tn+3
tn+4