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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
604
Order Number: 306262-004US
The timing parameters for DDR writes are defined in
. Both Write to Read
(IXP45X/IXP46X network processors: t
WTRD
) and Write to Command (IXP45X/IXP46X
network processors: t
WTCMD
) are defined in much the same manner, both accounting
for Write Latency (JEDEC: tWL) and Burst Length (JEDEC: BL). The difference lies in
the compensation for Write Recovery (JEDEC: t
WR
) and Write to Read (JEDEC: t
WTR
).
Note:
Burst Length is fixed at four for the IXP45X/IXP46X network processors.
Note:
The MCU allows for back-to-back Writes, so long as they are to an open page.
Figure 111. MCU DDR Read Command to Next Command Timing Diagram
Notes:
1.
Nominal t
DQSS
assumed
2.
t
RTW
= first pos. clock after last Data
3.
Burst Reads cannot interrupt the previous Read
4.
PRECHARGE cannot interrupt READ (DDRI/II)
B4216-001
m_clk
CMD
BL=4, CAS=2
0 1 2 3
DDRII,
BL=4, CAS=4
t
RTCMD
=t
RTW
t
RTW
=(CAS + (BL/2) + t
REG
Read Duration Equations (round up for
EX
A
EX
B
t
RDTW
t
RTCMD
=t
RDTW
Example A: BL=4, CAS=2
t
RTCMD
=(2+(4/2))=4
t
RDTW
=tRTCMD=4
R
Example B: DDRII, BL=4,
CAS=4
t
RTCMD
=(4+(4/2))=6
t
RDTW
=tRTCMD=6
Programming Examples:
CAS=2
CAS=4
non-integer results):
Next Allowed CMD: non-reg, DDRI, BL=4, CAS=2
Next Allowed CMD:
n on-reg, D DRII, BL=4, CAS=4
t0
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
0 1 2 3