DATA-RETENTION MODE The DS1265W provides full functional capability for Vcc greater than 3.OV and write protects by 2.8V. Data is maintained in the absence of Vcc without any additional support circuitry. The nonvolatile static RAMs constantly monitor Vcc. Should the supply voltage decay, the NV SRAMs automatically write protect themselves, all inputs become "don't care," and all outputs become high-impedance. As Vcc falls below approximately 2.5V, a power-switching circuit connects the lithium energy source to RAM to retain data. During power-up, when Vcc rises above approximately 2.5V, the power-switching circuit connects external Vcc to RAM and disconnects the lithium energy source. Normal RAM operation can resume after Vcc exceeds 3.OV.
| Control Voltage Input | Attenuation |
| V1 16 dB | V2 8dB | V3 4dB | V4 2dB | V5 1 dB | State RFl - RF2 |
| Low | Low | Low | Low | Low | Reference I.L. |
| Low | Low | Low | Low | High | 1 dB |
| Low | Low | Low | High | Low | 2dB |
| Low | Low | High | Low | Low | 4dB |
| Low | High | Low | Low | Low | 8dB |
| High | Low | Low | Low | Low | 16 dB |
| High | High | High | High | High | 31 dB Max. Atten. |
| Any combination of the above states will provide an attenuation approximately equal to the sum of the bits selected. |
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