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2.2 Memory Organization
SPRUGZ3A—May 2011
KeyStone Architecture External Memory Interface (EMIF16) User Guide
2-3
Chapter 2—Architecture
www.ti.com
2.2 Memory Organization
For information describing the device memory organization, see the device-specific
data manual.
2.3 Supported Modes
The EMIF16 module supports asynchronous interface with ASRAM, NAND and NOR.
2.4 Configuring the EMIF16 for Asynchronous Access
EMIF16 can operate in the following modes:
•
WE Strobe Mode
•
Select Strobe Mode
EMIF16 is clocked at CPU/6 frequency. So, for a device running at 1GHz, EMIF16 is
clocked at 166.67 MHz. All references to clock/clock cycles are in terms of EMIF16
clock cycles.
In WE Strobe mode, the byte enables EMIFBE[1:0] can be used as write strobes for the
current active chip select space. The EMIFCEx (x=0,1,2,3) chip select signal will remain
active throughout the duration of the asynchronous access. The main advantage of this
mode is that it allows two 8-bit devices to be connected to the same chip select. In this
mode, the bytes enables are connected to the write strobes of the two 8-bit devices. WE
strobe mode is the default mode supported on CE3. WE strobe mode is not supported
for CE0 - 2.
The Select Strobe (SS) mode is activated by setting the 'ss' bit in the Async Config
Register for the chip select under consideration. There is one Async Config Register for
each chip select. For more details on the Async Config Register, refer to
SS mode, the chip select acts as the strobe signal. So the chip select EMIFCEx will follow
EMIFOE for reads and EMIFWE for writes and is active only during the strobe period.
EMIFBE[1:0] act as byte enables. SS mode is supported for all 4 chip selects.
WE strobe mode cannot be used along with Select Strobe mode. Select Strobe mode
overrides WE Strobe mode.
EMIF16 also supports an Extended Wait mode that allows the device to extend the
strobe period beyond strobe cycles during an asynchronous access. Refer to
for more details on Extended Wait mode.