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4.2
Memory Interfaces Overview
4.2.1 DDR2 EMIF
4.2.2 External Memory Interface
4.2.2.1
Asynchronous EMIF (AEMIF)
Memory Interfaces Overview
This section describes the different memory interfaces of DM355.
DM355 supports several memory and external device interfaces, including the following:
•
DDR2 / mDDR Synchronous DRAM
•
Asynchronous EMIF
•
NAND Flash
•
OneNAND flash
The DDR2 EMIF interface, sometimes referred to as EMIF3.0 in DM355 documentation, is a dedicated
interface to DDR and MDDR SDRAM. It supports JESD79D-2A standard compliant DDR2 SDRAM
devices and supports only 16-bit interfaces.
DDR SDRAM plays a key role in a DM355-based system. Such a system is expected to require a
significant amount of high-speed external memory for the following:
•
Buffering input image data from sensors or video sources,
•
Intermediate buffering for processing/resizing of image data in the VPFE,
•
Numerous OSD display buffers
•
Intermediate buffering for large raw Bayer data image files while performing still camera processing
functions
•
Buffering for intermediate data while performing video encode and decode functions
•
Storage of executable firmware for the ARM
•
etc.
DM355’s External Memory Interface (EMIF) provides an 8-bit or 16-bit data bus, an address bus width of
up to 14-bits, and 2 dedicated chip selects, along with memory control signals. The EMIF module
supports:
•
Asynchronous memories (SRAM, Linear flash, etc.)
•
NAND flash memories
•
OneNAND flash memories
The Asynchronous EMIF (AEMIF) mode supports the following features:
•
SRAM on up to two asynchronous chip selects
•
Supports 8-bit or 16-bit data bus widths
•
Programmable asynchronous cycle timings
•
Supports extended waits
•
Supports Select Strobe mode
•
Supports booting DM355’s ARM processor from CE0 (e.g SRAM) via direct execution
SPRUFB3 – September 2007
Memory Mapping
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