S-25C080A H Series

22

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Write Protect Function during the Low Power Supply Voltage

The S-25C080A has a built-in detection circuit which operates with the low power supply voltage. The S-25C080A

cancels the Write operation (WRITE, WRSR) when the power supply voltage drops and power-on, at the same time,

goes in the Write protect status (WRDI) automatically to reset bit WEL. The detection voltage is 1.20 V typ., the

release voltage is 1.35 V typ., and its hysteresis is approx. 0.15 V (Refer to Figure 19).

To operate Write, after the power supply voltage dropped once but rose to the voltage level which allows Write again,

be sure to set the Write Enable Latch bit (WEL) before operating Write (WRITE, WRSR).

In the Write operation, data in the address written during the low power supply voltage is not assured.

Cancel the Write instruction

Set in Write protect (WRDI) automatically

Release voltage (

1.35 V Typ.

Hysteresis

approx. 0.15 V

Detection voltage (

1.20 V Typ.

Power supply voltage

Figure 19 Operation during Low Power Supply Voltage

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I/O Pin

1. Connection of input pin

All input pins in S-25C080A have the CMOS structure. Do not set these pins in high impedance during operation when

you design. Especially, set the CS input in the non-select status “H” during power-on/off and standby. The error Write

resistor of 10 k

Ω to 100 kΩ).

If the CS pin and the SCK pin change from “L” to “H” simultaneously, data may be input from the SI pin.

To prevent the error for sure, it is recommended to pull down the SCK pin to GND. In addition, it is recommended to

WP

2. Equivalent circuit of input and output pin

Figure 20 and 21 show the equivalent circuits of input pins in S-25C080A. A pull-up and pull-down elements are not

included in each input pin, pay attention not to set it in the floating state when you design.

Figure 22 shows the equivalent circuit of the output pin. This pin has the tri-state output of “H” level/“L” level/high

impedance.