FM1608 查看數據表（PDF） - Ramtron International Corporation
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FM1608 Datasheet PDF : 11 Pages
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Unlike other truly nonvolatile memory technologies,
there is no write delay with FRAM. Since the read
and write access times of the underlying memory are
the same, the user experiences no delay through the
bus. The entire memory operation occurs in a single
bus cycle. Therefore, any operation including read or
write can occur immediately following a write. Data
polling, a technique used with EEPROMs to
determine if a write is complete, is unnecessary.
Precharge Operation
The precharge operation is an internal condition that
prepares the memory for a new access. All memory
cycles consist of a memory access and a precharge.
The precharge is initiated by deasserting the /CE pin
high. It must remain high for at least the minimum
precharge time tPC.
The user dictates the beginning of this operation since
a precharge will not begin until /CE rises. However
the device has a maximum /CE low time specification
that must be satisfied.
FM1608
Endurance
The FM1608 internally operates with a read and
restore mechanism. Therefore, each read and write
cycle involves a change of state. The memory
architecture is based on an array of rows and
columns. Each read or write access causes an
endurance cycle for an entire row. In the FM1608, a
row is 32 bits wide. Every 4-byte boundary marks
the beginning of a new row. Endurance can be
optimized by ensuring frequently accessed data is
located in different rows. Regardless, FRAM offers
substantially higher write endurance than other
nonvolatile memories. The rated endurance limit of
1012 cycles will allow 3000 accesses per second to the
same row for 10 years.
Applications
As the first truly nonvolatile RAM, the FM1608 fits
into many diverse applications. Clearly, its monolithic
nature and high performance make it superior to
battery-backed SRAM in most every application. The
advantages of FRAM memory compared with battery-
backed SRAM include its immunity to humidity and
shock. Also FRAM is lower cost, has a smaller board
footprint, and eliminates the battery – a source of
environmental and field replacement concerns. The
FRAM Design Considerations section that follows
highlights the simple design considerations that
should be reviewed in both retrofit and new design
situations.
Rev. 3.0
Nov. 2004
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