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U630H16SA25G1 查看數據表(PDF) - Simtek Corporation

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U630H16SA25G1 HardStore 2K x 8 nvSRAM Simtek
Simtek Corporation Simtek
U630H16SA25G1 Datasheet PDF : 15 Pages
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U630H16
Device Operation
The U630H16 has two separate modes of operation:
SRAM mode and nonvolatile mode, determined by the
state of the NE pin. In SRAM mode, the memory opera-
tes as a standard fast static RAM. In nonvolatile mode,
data is transferred from SRAM to EEPROM (the
STORE operation) or from EEPROM to SRAM (the
RECALL operation). In this mode SRAM functions are
disabled.
SRAM READ
The U630H16 performs a READ cycle whenever E and
G are LOW while W and NE are HIGH. The address
specified on pins A0 - A10 determines which of the
2048 data bytes will be accessed. When the READ is
initiated by an address transition, the outputs will be
valid after a delay of tcR. If the READ is initiated by E or
G, the outputs will be valid at ta(E) or at ta(G), whichever
is later. The data outputs will repeatedly respond to
address changes within the tcR access time without the
need for transition on any control input pins, and will
remain valid until another address change or until E or
G is brought HIGH or W or NE is brought LOW.
SRAM WRITE
A WRITE cycle is performed whenever E and W are
LOW and NE is HIGH. The address inputs must be sta-
ble prior to entering the WRITE cycle and must remain
stable until either E or W goes HIGH at the end of the
cycle. The data on pins DQ0 - 7 will be written into the
memory if it is valid tsu(D) before the end of a W control-
led WRITE or tsu(D) before the end of an E controlled
WRITE.
It is recommended that G is kept HIGH during the en-
tire WRITE cycle to avoid data bus contention on the
common I/O lines. If G is left LOW, internal circuitry will
turn off the output buffers tdis(W) after W goes LOW.
Noise Consideration
The U630H16 is a high speed memory and therefore
must have a high frequency bypass capacitor of appro-
ximately 0.1 μF connected between VCC and VSS using
leads and traces that are as short as possible. As with
all high speed CMOS ICs, normal carefull routing of
power, ground and signals will help prevent noise pro-
blems.
Hardware Nonvolatile STORE
A STORE cycle is performed when NE, E and W are
LOW while G is HIGH. While any sequence to achieve
this state will initiate a STORE, only W initiation and E
initiation are practical without risking an unintentional
SRAM WRITE that would
STK Control #ML0036
disturb SRAM data. During a STORE cycle, previous
nonvolatile data is erased and the SRAM contents are
then programmed into nonvolatile elements. Once a
STORE cycle is initiated, further input and output is
disabled and the DQ0 - 7 pins are tristated until the
cycle is completed.
If E and G are LOW and W and NE are HIGH at the
end of the cycle, a READ will be performed and the out-
puts will go active, indicating the end of the STORE.
Hardware Nonvolatile RECALL
A RECALL cycle is performed when E, G and NE are
LOW while W is HIGH. Like the STORE cycle, RECALL
is initiated when the last of the three clock-signals goes
to the RECALL state. Once initiated, the RECALL cycle
will take „RECALL Cycle Time“ to complete, during
which all inputs are ignored. When the RECALL com-
pletes, any READ or WRITE state on the input pins will
take effect.
Internally, RECALL is a two step procedure. First, the
SRAM data is cleared and second, the nonvolatile
information is transferred into the SRAM cells. The
RECALL in no way alters the data in the nonvolatile
cells. The nonvolatile data can be recalled an unlimited
number of times.
Like the STORE cycle, a transition must occur on some
control pins to cause a RECALL, preventing inadver-
tend multi-triggering.
Automatic Power Up RECALL
On power up, once VCC exceeds the sense voltage of
VSWITCH, a RECALL cycle is automatically initiated. The
voltage on the VCC pin must not drop below VSWITCH
once it has risen above it in order for the RECALL to
operate properly. Due to this automatic RECALL,
SRAM operation cannot commence until tRESTORE after
VCC exceeds VSWITCH. If the U630H16 is in a WRITE
state at the end of power up RECALL, the SRAM data
will be corrupted.
To help avoid this situation, a 10 KΩ resistor should be
connected between W and system VCC.
Hardware Protection
The U630H16 offers two levels of protection to sup-
press inadvertent STORE cycles. If the control signals
(E, G, W and NE) remain in the STORE condition at the
end of a STORE cycle, a second STORE cycle will not
be started. The STORE (or RECALL) will be initiated
only after a transition on any one of these signals to the
required state. In addition to multi-trigger protection, the
U630H16 offers hardware protection through VCC
Sense. When VCC < VSWITCH the externally initiated
STORE operation will be inhibited.
12
Rev 1.0
March 31, 2006
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