MDDR Subsystem
Microsemi Proprietary UG0446 User Guide Revision 7.0
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•
The DDR controller keeps the DDR memory devices in Self-refresh mode whenever the self refresh
is enabled and the
register bit is set and no reads or writes are pending
in the controller.
•
The controller takes the DDR memory out of Self-refresh mode whenever the
REG_DDRC_SELFREF_EN input is deasserted or new commands are received by the controller.
•
When the DDR self refresh is enabled, the DDR I/O bank may go into recalibration and a glitch may
occur in the MDDR bank I/Os, which are being used for general purpose rather than for the DDR
memory. The DDR I/Os ODT is periodically calibrated for PVT changes and will be effected only
when the I/Os are in tri state (DDR I/Os are tri stated only in self-refresh mode).
Deep Power-Down (LPDDR1)
•
This is supported only for LPDDR1. The DDR controller puts the DDR SDRAM devices in deep
power-down mode whenever the
bit is set and no reads or
writes are pending in the DDR controller.
•
The DDR controller automatically exits deep power-down mode and reruns the initialization
sequence when the REG_DDRC_DEEPPOWERDOWN_EN bit is reset to 0. The contents of DDR
memory may lost upon entry into deep power-down mode.
3.5.4.3.6
DRAM Initialization
After Reset, the DDR controller initializes DDR memories through an initialization sequence, depending
on the type of DDR memory used. For more information on the initialization process, refer to the JEDEC
specification.
3.5.5
MDDR Subsystem Features Configuration
The MDDR subsystem registers must be initialized before accessing DDR memory through the MDDR
subsystem. When using the
System Builder
flow through Libero SoC, all of the necessary registers are
initialized automatically by the resulting module.
This section provides the registers features of the MDDR. All registers are listed with their bit definitions
in the
"MDDR Configuration Registers" section on page 61
section.
3.5.5.1
Memory Type
must be configured to select the memory type (DDR2, DDR3, or LPDDR1) to access
from MDDR subsystem.
3.5.5.2
Bus Width Configurations
The MDDR supports various bus widths listed in the following table. The MDDR can be programmed to
work in full, half, or quarter bus width mode by configuring the
registers when the controller is in soft reset.
3.5.5.3
Burst Mode
The DDR controller performs the burst write operations to DDR memory, depending on the burst mode
selection. Burst mode is selected as sequential or interleaving by configuring
to 1 or 0. Burst length can be selected as 4, 8, or 16 by configuring
.
Table 12 •
Supported Bus Widths
Bus Width
M2GL005/M2GL010/M2GL025/
M2GL090
M2GL050
(FCS325, VF400,
FG484)
M2GL050
(FG896)
M2GL150 (FC1152)
Full bus width
–
✓
✓
Half bus width
✓
✓
✓
✓
Quarter bus width
✓
✓