MDDR Subsystem
Microsemi Proprietary UG0446 User Guide Revision 7.0
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command from DDR Controller after the ACTIVATE command for the same bank prior to tRCD
(MIN). This configuration is part of DDR2 Extended Mode register and DDR3 mode register1.
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CAS Write Latency (CWL) is defined by DDR3 MR2[5:3] and is the delay in clock cycles from
the releasing of the internal write to the latching of the first data in. The overall WRITE latency
(WL) is equal to CWL + AL (by default CWL is set to 5 clock cycles).
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Select the following ZQ Calibration settings for DDR3 memory. For more details, refer to
Calibration" section on page 17
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Zqinit
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ZQCS
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ZQCS Interval
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Select the other following settings.
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The local ODT setting is not supported for LPDDR memory. For the DDR2/DDR3 memory type,
the user can choose any option for “Local ODT”. User can enable or disable “LOCAL ODT”
during read transaction.
•
Drive strength setting is defined by EMR[7:5] register bits of LPDDR memory with drop down
options of `Full', `Half', `Quarter', and `One-eighth' drive strength; EMR[1] register bit of DDR2
memory with drop down options of `Full' and `Weak' drive strength; and MR1 register bits M5
and M1 of DDR3 memory with drop down options of `RZQ/6' and `RZQ/7'.
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The partial array self-refresh coverage setting is defined by EMR[2:0] register bits of LPDDR
memory with drop down options of `Full', `Quarter', `One-eighth', and `One-sixteenth'. This
feature improves power savings by selecting the amount of memory to be refreshed during self-
refresh.
•
R
TT
(Nominal) setting is defined by EMR[6] and EMR[2] register bits of DDR2 memory, which
determines what ODT resistance is enabled with drop down options of `RTT disabled', '50
ohms', '75 Ω', and `150 Ω’, and it is defined by MR1[9], MR1[6] and MR1[2] register bits of
DDR3 memory. In DDR3 memory, RTT nominal termination is allowed during standby
conditions and WRITE operations, not during READ operations with drop down options of
`RZQ/2', `RZQ/4' and `RZQ/6'.
•
R
TT
_WR (Dynamic ODT) setting is defined by MR2[10:9] register bits of DDR3 memory. This is
applicable only during WRITE operations. If dynamic ODT (Rtt_WR) is enabled, DRAM
switches from normal ODT (R
TT_nom
) to dynamic ODT (Rtt_WR) when beginning WRITE burst
and subsequently switches back to normal ODT at the end of WRITE burst. The drop down
options provided to the user are `off', `RZQ/4', and `RZQ/2'.
•
The auto self-refresh setting is defined by MR2[6] register bit of DDR3 memory with drop down
options `Manual' and `Auto'. The self-refresh temperature setting is defined by MR2[7] register
bit of DDR2 memory with drop down options of `Normal' and `Extended'.