Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262-004US
613
Memory Controller—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
• Once the refresh timer expires, the MCU knows that a refresh cycle is necessary.
— The refresh timer continues to count for the next refresh cycle.
• The MARB allows the current transaction to complete.
— If the DDRI SDRAM Control Block and the DDRI SDRAM array are transferring
data, or a CMTQ tenure is ongoing, the refresh cycle is queued until the
transaction is complete or the CMTQ tenure expires.
• The DDRI SDRAM Control Block closes all open pages with a
precharge-all
command
to all the populated DDRI SDRAM banks.
— The DDRI SDRAM Control Block resets the page register valid bits.
• The DDRI SDRAM Control Block issues
auto-refresh
command to DDRI SDRAM
bank 0.
— This command affects all internal leaves.
• In the next cycle, the DDRI SDRAM Control Block issues
auto-refresh
command to
DDRI SDRAM bank 1.
— The MCUs internal 2-bit refresh counter is decremented by one. This is actually
done when the DDRSM consumes the command from the ARB.
Figure 117. Refresh While the Memory Bus is Not Busy
A7799-02
CKE
CK
CK_N
Command
A0-A8
DQS
Valid
Valid
t
CH
t
CK
t
RP
t
CL
t
RFC
t
RFC
t
IS
t
IH
NOP
PRE
NOP
NOP
NOP
AR
NOP
AR
NOP
ACT
t
IS
t
IH
t
IS
t
IH
DQ
DM
RA
A9, A11, A12
RA
A10
RA
All Banks
BA0, BA1
RA
One Bank
Bank(s)
Notes:
PRE = Precharge; ACT = Active; RA = Row address; BA = Bank address; AR = Autorefresh
NOP commands are shown for ease of illustration; other valid commands may be possible at these times.
DM, DQ, and DQS signals are all don't care/high-Z operations shown.
= Don't Care