Cypress CY14B108M, CY14B108K manual Device Operation, Sram Read, Sram Write, AutoStore Operation

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PRELIMINARY

CY14B108K, CY14B108M

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1. Pin Definitions (continued)

 

 

 

 

 

 

 

 

 

Pin Name

I/O Type

 

 

 

 

Description

 

 

INT

Output

Interrupt Output. Programmable to respond to the clock alarm, the watchdog timer, and the power

 

 

monitor. Also programmable to either active HIGH (push or pull) or LOW (open drain).

 

 

 

 

 

VSS

Ground

Ground for the Device. Must be connected to ground of the system.

 

VCC

Power Supply

Power Supply Inputs to the Device. 3.0V +20%, –10%.

 

 

 

 

Input/Output

Hardware STORE Busy

(HSB)

. When LOW this output indicates that a Hardware STORE is in progress.

 

HSB

 

 

When pulled LOW external to the chip it initiates a nonvolatile STORE operation. A weak internal pull

 

 

 

 

up resistor keeps this pin HIGH if not connected (connection optional). After each STORE operation

 

 

 

 

HSB is driven HIGH for short time with standard output high current.

VCAP

Power Supply

AutoStore Capacitor. Supplies power to the nvSRAM during power loss to store data from SRAM to

 

 

 

 

nonvolatile elements.

 

Device Operation

The CY14B108K/CY14B108M nvSRAM is made up of two functional components paired in the same physical cell. These are a SRAM memory cell and a nonvolatile QuantumTrap cell. The SRAM memory cell operates as a standard fast static RAM. Data in the SRAM is transferred to the nonvolatile cell (the STORE operation), or from the nonvolatile cell to the SRAM (the RECALL operation). Using this unique architecture, all cells are stored and recalled in parallel. During the STORE and RECALL operations SRAM read and write operations are inhibited. The CY14B108K/CY14B108M supports infinite reads and writes similar to a typical SRAM. In addition, it provides infinite RECALL operations from the nonvolatile cells and up to 200K STORE operations. See the Truth Table For SRAM Operations on page 24 for a complete description of read and write modes.

SRAM Read

The CY14B108K/CY14B108M performs a read cycle whenever CE and OE are LOW, and WE and HSB are HIGH. The address specified on pins A0-19or A0-18determines which of the 1,048,576 data bytes or 524,288 words of 16 bits each are accessed. Byte enables (BHE, BLE) determine which bytes are enabled to the output, in the case of 16-bit words. When the read is initiated by an address transition, the outputs are valid after a delay of tAA (read cycle 1). If the read is initiated by CE or OE, the outputs are valid at tACE or at tDOE, whichever is later (read cycle 2). The data output repeatedly responds to address changes within the tAA access time without the need for transi- tions on any control input pins. This remains valid until another address change or until CE or OE is brought HIGH, or WE or HSB is brought LOW.

SRAM Write

A write cycle is performed when CE and WE are LOW and HSB is HIGH. The address inputs must be stable before entering the write cycle and must remain stable until CE or WE goes HIGH at the end of the cycle. The data on the common I/O pins DO0-15are written into the memory if it is valid tSD before the end of a WE controlled write or before the end of a CE controlled write. The Byte Enable inputs (BHE, BLE) determine which bytes are written, in the case of 16-bit words. Keep OE HIGH during the entire write cycle to avoid data bus contention on common I/O lines. If OE is left LOW, internal circuitry turns off the output buffers tHZWE after WE goes LOW.

Document #: 001-47378 Rev. **

AutoStore Operation

The CY14B108K/CY14B108M stores data to the nvSRAM using one of three storage operations. These three operations are: Hardware STORE, activated by the HSB; Software STORE, activated by an address sequence; AutoStore, on device power down. The AutoStore operation is a unique feature of QuantumTrap technology and is enabled by default on the CY14B108K/CY14B108M.

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 2. AutoStore Mode

Vcc

0.1uF

10kOhm

Vcc

 

WEVCAP

VSS VCAP

Figure 2 shows the proper connection of the storage capacitor (VCAP) for automatic STORE operation. Refer to DC Electrical Characteristics on page 15 for the size of the VCAP. The voltage on the VCAP pin is driven to VCC by a regulator on the chip. A pull up should be placed on WE to hold it inactive during power up. This pull up is only effective if the WE signal is tri-state during power up. Many MPUs tri-state their controls on power up. Verify this when using the pull up. When the nvSRAM comes out of

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Contents Cypress Semiconductor Corporation FeaturesLogic Block Diagram1, 2 Functional DescriptionPinouts AutoStore Operation Device OperationSram Read Sram WriteSoftware Store Hardware Recall Power UpHardware Store HSB Operation Software RecallStore Mode SelectionA15 A05 Mode Power Preventing AutoStoreNoise Considerations Data Protection Best PracticesReal Time Clock Operation Alarm Watchdog TimerCalibrating the Clock Flags Register Power MonitorInterrupt Register InterruptsAF Alarm Flag WDF Watchdog Timer FlagPF Power Fail Flag PFE Power Fail EnableOscen WDSWDF Oscf For the register is 0 to 0xFFFF9 0x7FFF9 Time Keeping Seconds0xFFFF6 0x7FFF6 Interrupt Status/Control 0xFFFF5 0x7FFF5 Alarm DayTime-base Write only. Reading it always returns aThis condition and write 0 to clear this flag 0xFFFF2 0x7FFF2 Alarm SecondsCenturies 0xFFFF0 0x7FFF0 Flags WatchdogOperating Range DC Electrical CharacteristicsRange Ambient Temperature Maximum RatingsAC Test Conditions Data Retention and EnduranceCapacitance Thermal ResistanceRTC Capacitor Pin Voltage TOCS RTC Oscillator Time to Start RTC Backup CurrentHot Temperature 85 oC RTC Battery Pin VoltageSram Write Cycle AC Switching CharacteristicsSwitching Waveforms Parameters Sram Read CycleData Input Input Data Valid Data Output High Impedance Output Data ValidStandby Active Address Address ValidData Input Input Data Valid High Impedance Data Output Data Input Data OutputInput Data Valid High Impedance Not applicable for RTC register writesParameters Description 20 ns 25 ns 45 ns Unit Min Max AutoStore/Power Up RecallSoftware Controlled Store and Recall Cycle Hardware Store Pulse Width To Output Active Time when write latch not setHardware Store Cycle Description 20 ns 25 ns 45 ns Unit MinTruth Table For Sram Operations For x8 ConfigurationFor x16 Configuration Inputs and Outputs Mode PowerPart Numbering Nomenclature CY14 B 108 K ZS P 20 X C T ZS TsopNvsram Ordering Information Pin Tsop II Package Diagrams51-85160 Document History Sales, Solutions, and Legal InformationWorldwide Sales and Design Support Products PSoC Solutions New Data Sheet
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