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CY7C1526KV18 Datasheet(PDF) 9 Page - Cypress Semiconductor |
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CY7C1526KV18 Datasheet(HTML) 9 Page - Cypress Semiconductor |
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9 / 31 page  CY7C1511KV18, CY7C1526KV18 CY7C1513KV18, CY7C1515KV18 Document Number: 001-00435 Rev. *G Page 9 of 31 Single Clock Mode The CY7C1511KV18 is used with a single clock that controls both the input and output registers. In this mode the device recognizes only a single pair of input clocks (K and K) that control both the input and output registers. This operation is identical to the operation if the device had zero skew between the K/K and C/C clocks. All timing parameters remain the same in this mode. To use this mode of operation, the user must tie C and C HIGH at power on. This function is a strap option and not alterable during device operation. Concurrent Transactions The read and write ports on the CY7C1513KV18 operate independently of one another. As each port latches the address inputs on different clock edges, the user can read or write to any location, regardless of the transaction on the other port. If the ports access the same location when a read follows a write in successive clock cycles, the SRAM delivers the most recent information associated with the specified address location. This includes forwarding data from a write cycle that was initiated on the previous K clock rise. Read access and write access must be scheduled such that one transaction is initiated on any clock cycle. If both ports are selected on the same K clock rise, the arbitration depends on the previous state of the SRAM. If both ports are deselected, the read port takes priority. If a read was initiated on the previous cycle, the write port takes priority (as read operations cannot be initiated on consecutive cycles). If a write was initiated on the previous cycle, the read port takes priority (as write operations cannot be initiated on consecutive cycles). Therefore, asserting both port selects active from a deselected state results in alter- nating read or write operations being initiated, with the first access being a read. Depth Expansion The CY7C1513KV18 has a port select input for each port. This enables for easy depth expansion. Both port selects are sampled on the rising edge of the positive input clock only (K). Each port select input can deselect the specified port. Deselecting a port does not affect the other port. All pending transactions (read and write) are completed before the device is deselected. Programmable Impedance An external resistor, RQ, must be connected between the ZQ pin on the SRAM and VSS to allow the SRAM to adjust its output driver impedance. The value of RQ must be 5X the value of the intended line impedance driven by the SRAM, the allowable range of RQ to guarantee impedance matching with a tolerance of ±15% is between 175 Ω and 350Ω, with VDDQ =1.5V. The output impedance is adjusted every 1024 cycles upon power up to account for drifts in supply voltage and temperature. Echo Clocks Echo clocks are provided on the QDR II to simplify data capture on high speed systems. Two echo clocks are generated by the QDR II. CQ is referenced with respect to C and CQ is referenced with respect to C. These are free running clocks and are synchro- nized to the output clock of the QDR II. In the single clock mode, CQ is generated with respect to K and CQ is generated with respect to K. The timing for the echo clocks is shown in the Switching Characteristics on page 25. PLL These chips use a PLL that is designed to function between 120 MHz and the specified maximum clock frequency. During power up, when the DOFF is tied HIGH, the PLL is locked after 20 μs of stable clock. The PLL can also be reset by slowing or stopping the input clocks K and K for a minimum of 30 ns. However, it is not necessary to reset the PLL to lock to the desired frequency. The PLL automatically locks 20 μs after a stable clock is presented. The PLL may be disabled by applying ground to the DOFF pin. When the PLL is turned off, the device behaves in QDR I mode (with one cycle latency and a longer access time). [+] Feedback |
Similar Part No. - CY7C1526KV18 |
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Similar Description - CY7C1526KV18 |
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