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FM21L16 Datasheet(PDF) 8 Page - Ramtron International Corporation |
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FM21L16 Datasheet(HTML) 8 Page - Ramtron International Corporation |
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8 / 15 page  FM21L16 - 128Kx16 FRAM Rev. 2.0 Apr. 2011 Page 8 of 15 SRAM Drop-In Replacement The FM21L16 has been designed to be a drop-in replacement for standard asynchronous SRAMs. The device does not require /CE to toggle for each new address. /CE may remain low for as long as 10µs. While /CE is low, the device automatically detects address changes and a new access is begun. It also allows page mode operation at speeds up to 33MHz. The user must be sure /CE is not low at powerup or powerdown events. If /CE and /WE are both low during power cycles, data corruption will occur. Figure 6 shows a pullup resistor on /CE which will keep the pin high during power cycles assuming the MCU/MPU pin is tri-stated during the system reset. The pullup resistor value should be chosen to ensure the /CE pin tracks VDD yet a high enough value that the current drawn when /CE is low is not an issue. A 10K ohm resistor draws 330µA when /CE is low and VDD=3.3V. Figure 6. Use of Pullup Resistor on /CE For applications that require the lowest power consumption, the /CE signal should be active (low) only during memory accesses. The FM21L16 draws supply current while /CE is low, even if addresses and control signals are static. While /CE is high, the device draws no more than the maximum standby current ISB. The FM21L16 is backward compatible with the 1Mbit FM20L08 and 256Kbit FM18L08 devices. That is, operating the FM21L16 with /CE toggling low on every address is perfectly acceptable. The /UB and /LB byte select pins are active for both read and write cycles. They may be used to allow the device to be wired as a 256Kx8 memory. The upper and lower data bytes can be tied together and controlled with the byte selects. Individual byte enables or the next higher address line A(17) may be available from the system processor. Figure 7. FM21L16 Wired as 256Kx8 CE WE OE A(16:0) DQ FM21L16 MCU/ MPU VDD R |
Similar Part No. - FM21L16 |
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Similar Description - FM21L16 |
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