Device Operation
The
SRAM Read
The
SRAM Write
A Write cycle is performed whenever CE and WE are LOW and HSB is HIGH. The address inputs must be stable prior to entering the Write cycle and must remain stable until either CE or WE goes HIGH at the end of the cycle. The data on the common IO pins
AutoStore Operation
The
1.Hardware store activated by HSB
2.Software store activated by an address sequence
3.AutoStore on device power down
AutoStore operation is a unique feature of QuantumTrap technology and is enabled by default on the
Document Number:
During normal operation, the device draws current from VCC to charge a capacitor connected to the VCAP pin. This stored charge is used by the chip to perform a single STORE operation. If the voltage on the VCC pin drops below VSWITCH, the part automatically disconnects the VCAP pin from VCC. A STORE operation is initiated with power provided by the VCAP capacitor.
Figure 3 shows the proper connection of the storage capacitor (VCAP) for automatic store operation. A charge storage capacitor between 68 µF and 220 µF (+20%) rated at 6V must be provided. The voltage on the VCAP pin is driven to 5V by a charge pump internal to the chip. A pull up is placed on WE to hold it inactive during power up.
Figure 3. AutoStore Mode
9&$3 | 9FF | N2KP | N2KP |
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| +6% |
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5) Y |
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| 5) %\SDVV |
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9VV
In system power mode, both VCC and VCAP are connected to the +5V power supply without the 68 μF capacitor. In this mode, the AutoStore function of the
To reduce unnecessary nonvolatile stores, AutoStore, and Hardware Store operations are ignored, unless at least one Write operation has taken place since the most recent STORE or RECALL cycle. Software initiated STORE cycles are performed regardless of whether a Write operation has taken place. An optional pull up resistor is shown connected to HSB. The HSB signal is monitored by the system to detect if an AutoStore cycle is in progress.
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