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X20C05JM-55 Datasheet(PDF) 3 Page - Xicor Inc. |
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X20C05JM-55 Datasheet(HTML) 3 Page - Xicor Inc. |
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3 / 19 page  X20C05 3 DEVICE OPERATION The CE, OE, WE and NE inputs control the X20C05 operation. The X20C05 byte-wide NOVRAM uses a 2-line control architecture to eliminate bus contention in a system environment. The I/O bus will be in a high impedance state when either OE or CE is HIGH, or when NE is LOW. RAM Operations RAM read and write operations are performed as they would be with any static RAM. A read operation requires CE and OE to be LOW with WE and NE HIGH. A write operation requires CE and WE to be LOW with NE HIGH. There is no limit to the number of read or write operations performed to the RAM portion of the X20C05. MEMORY TRANSFER OPERATIONS There are two memory transfer operations: a recall operation whereby the data stored in the E2PROM array is transferred to the RAM array; and a store operation which causes the entire contents of the RAM array to be stored in the E2PROM array. Recall operations are performed automatically upon power-up and under host system control when NE, OE and CE are LOW and WE is HIGH. The recall operation takes a maximum of 5 µs. There are two methods of initiating a store operation. The first is the software store command. This command takes the place of the hardware store employed on the X20C04. This command is issued by entering into the special command mode: NE, CE, and WE strobe LOW while at the same time a specific address and data combination is sent to the device. This is a three step operation: the first address/data combination is 155[H]/AA[H]; the second combination is 0AA[H]/55[H]; and the final command combination is 155[H]/33[H]. This sequence of pseudo write operations will immedi- ately initiate a store operation. Refer to the software command timing diagrams for details on set and hold times for the various signals. The second method of storing data is through the AUTOSTORE command. When enabled, data is auto- matically stored from the RAM into the E2PROM array whenever VCC falls below the preset AUTOSTORE threshold. This feature is enabled by performing the first two steps for the software store with the command combination being 155[H]/CC[H]. The AUTOSTORE feature is disabled by issuing the three step command sequence with the command com- bination being 155[H]/CD[H]. The AUTOSTORE feature will also be reset if VCC falls below the power-up reset threshold (approximately 3.5V) and is then raised back into the operating range. DATA PROTECTION The X20C05 supports two methods of protecting the nonvolatile data. —If after power-up the AUTOSTORE feature is not enabled, no AUTOSTORE can occur. —If after power-up no RAM write operations have oc- curred no store operation can be initiated. The software store and AUTOSTORE commands will be ignored. SYMBOL TABLE WAVEFORM INPUTS OUTPUTS Must be steady Will be steady May change from LOW to HIGH Will change from LOW to HIGH May change from HIGH to LOW Will change from HIGH to LOW Don’t Care: Changes Allowed Changing: State Not Known N/A Center Line is High Impedance |
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Similar Description - X20C05JM-55 |
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