DS2251 データシートの表示（PDF） - Dallas Semiconductor -> Maxim Integrated
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DS2251 Datasheet PDF : 20 Pages
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DS2251T MEMORY MAP WITH (PES=1) Figure 4
DS2251T
POWER MANAGEMENT
The DS2251T monitors VCC to provide Power-fail Reset, early warning Power-fail Interrupt, and switch-
over to lithium backup. It uses an internal band-gap reference in determining the switch points. These are
called VPFW, VCCMIN, and VLI respectively. When VCC drops below VPFW, the DS2251T will perform an
interrupt vector to location 2Bh if the power-fail warning is enabled. Full processor operation continues
regardless. When power falls further to VCCMIN, the DS2251T invokes a reset state. No further code
execution will be performed unless power rises back above VCCMIN. All decoded chip enables and the
R/ W signal go to an inactive (logic 1) state. The VRST signal will be driven to a logic 0. VCC is still the
power source at this time. When VCC drops further to below VLI, internal circuitry will switch to the built-
in lithium cell for power. The majority of internal circuits will be disabled and the remaining nonvolatile
states will be retained. PF will be driven to a logic 0. The User’s Guide has more information on this
topic. The trip points VCCMIN and VPFW are listed in the electrical specifications.
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