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CY14B512Q1A-SXIT Datasheet(PDF) 5 Page - Cypress Semiconductor |
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CY14B512Q1A-SXIT Datasheet(HTML) 5 Page - Cypress Semiconductor |
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5 / 32 page  CY14C512Q CY14B512Q CY14E512Q Document Number: 001-65267 Rev. *D Page 5 of 32 indicated by HSB being pulled LOW or RDY bit being set to ‘1’. To avoid 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. However, software initiated STORE cycles are performed regardless of whether a write operation has taken place. AutoStore Operation The AutoStore operation is a unique feature of nvSRAM which automatically stores the SRAM data to QuantumTrap cells during power-down. This STORE makes use of an external capacitor (VCAP) and enables the device to safely STORE the data in the nonvolatile memory when power goes down. During normal operation, the device draws current from VCC to charge the capacitor connected to the VCAP pin. When the voltage on the VCC pin drops below VSWITCH during power-down, the device inhibits all memory accesses to nvSRAM and automatically performs a conditional STORE operation using the charge from the VCAP capacitor. The AutoStore operation is not initiated if no write cycle has been performed since last RECALL. Note If a capacitor is not connected to VCAP pin, AutoStore must be disabled by issuing the AutoStore Disable instruction (AutoStore Disable (ASDISB) Instruction on page 15). If AutoStore is enabled without a capacitor on the VCAP pin, the device attempts an AutoStore operation without sufficient charge to complete the STORE. This will corrupt the data stored in nvSRAM, Status Register as well as the serial number and it will unlock the SNL bit. To resume normal functionality, the WRSR instruction must be issued to update the nonvolatile bits BP0, BP1, and WPEN in the Status Register. Figure 3 shows the proper connection of the storage capacitor (VCAP) for AutoStore operation. Refer to DC Electrical Charac- teristics on page 20 for the size of the VCAP. Note CY14X512Q1A does not support AutoStore operation. You must perform Software STORE operation by using the SPI STORE instruction to secure the data. Figure 3. AutoStore Mode Software STORE Operation Software STORE enables the user to trigger a STORE operation through a special SPI instruction. STORE operation is initiated by executing STORE instruction irrespective of whether a write has been performed since the last NV operation. A STORE cycle takes tSTORE time to complete, during which all the memory accesses to nvSRAM are inhibited. The RDY bit of the Status Register or the HSB pin may be polled to find the Ready or Busy status of the nvSRAM. After the tSTORE cycle time is completed, the SRAM is activated again for read and write operations. Hardware STORE and HSB pin Operation The HSB pin in CY14X512Q3A is used to control and acknowledge STORE operations. If no STORE or RECALL is in progress, this pin can be used to request a Hardware STORE cycle. When the HSB pin is driven LOW, nvSRAM conditionally initiates a STORE operation after tDELAY duration. A STORE cycle starts only if a write to the SRAM has been performed since the last STORE or RECALL cycle. Reads and Writes to the memory are inhibited for tSTORE duration or as long as HSB pin is LOW. The HSB pin also acts as an open drain driver (internal 100 k weak pull up resistor) that is internally driven LOW to indicate a busy condition when the STORE (initiated by any means) is in progress. Note After each Hardware and Software STORE operation HSB is driven HIGH for a short time (tHHHD) with standard output high current and then remains HIGH by an internal 100 k pull up resistor. Note For successful last data byte STORE, a hardware STORE should be initiated at least one clock cycle after the last data bit D0 is received. Upon completion of the STORE operation, the nvSRAM memory access is inhibited for tLZHSB time after HSB pin returns HIGH. The HSB pin must be left unconnected if not used. Note CY14X512Q1A/CY14X512Q2A do not have HSB pin. RDY bit of the SPI Status Register may be probed to determine the Ready or Busy status of nvSRAM. RECALL Operation A RECALL operation transfers the data stored in the nonvolatile QuantumTrap elements to the SRAM. A RECALL may be initiated in two ways: Hardware RECALL, initiated on power-up and Software RECALL, initiated by a SPI RECALL instruction. Internally, RECALL is a two step procedure. First, the SRAM data is cleared. Next, the nonvolatile information is transferred into the SRAM cells. All memory accesses are inhibited while a RECALL cycle is in progress. The RECALL operation does not alter the data in the nonvolatile elements. Hardware RECALL (Power-Up) During power-up, when VCC crosses VSWITCH, an automatic RECALL sequence is initiated, which transfers the content of nonvolatile memory on to the SRAM. The data would previously have been stored on the nonvolatile memory through a STORE sequence. A Power-Up RECALL cycle takes tFA time to complete and the memory access is disabled during this time. HSB pin is used to detect the ready status of the device. 0.1 uF VCC VCAP CS VCAP VSS VCC |
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