Maxim specifications DS5001FP Connection to 64k x 8 Sram, Power Management

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DS5001FP

Figure 6. DS5001FP CONNECTION TO 64k x 8 SRAM

POWER MANAGEMENT

The DS5001FP monitors VCC to provide power-fail reset, early warning power-fail interrupt, and switch over to lithium backup. It uses an internal bandgap reference in determining the switch points. These are

called VPFW, VCCMIN, and VLI, respectively. When VCC drops below VPFW, the DS5001FP performs an interrupt vector to location 2Bh if the power-fail warning was enabled. Full processor operation continues

regardless. When power falls further to VCCMIN, the DS5001FP invokes a reset state. No further code

execution is performed unless power rises back above VCCMIN. All decoded chip enables and the R/ W signal go to an inactive (logic 1) state. VCC is still the power source at this time. When VCC drops further

to below VLI, internal circuitry switches to the lithium cell for power. The majority of internal circuits are disabled and the remaining nonvolatile states are retained. Any devices connected VCCO are powered by the lithium cell at this time. VCCO is at the lithium battery voltage minus approximately 0.45V. This drop varies depending on the load. Low power SRAMs should be used for this reason. When using the DS5001FP, the user must select the appropriate battery to match the RAM data retention current and the desired backup lifetime. Note that the lithium cell is only loaded when VCC < VLI. The User’s Guide has more information on this topic. The trip points VCCMIN and VPFW are listed in Electrical Specifications.

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Contents Features DS5001FP 128k Soft Microprocessor ChipDescription Ordering InformationBlock Diagram Signal Description Mqfp PIN DescriptionMsel Instruction SET Memory OrganizationMemory MAP in Partitionable Mode PM = Memory MAP with PES = Connection to 128k x 8 Sram Power Management DS5001FP Connection to 64k x 8 SramDC Characteristics Absolute Maximum RatingsDC Characteristics AC Characteristics Expanded BUS Mode Timing Specifications MAX UnitsDS5001FP Expanded DATA-MEMORY Write Cycle External Clock Drive External Clock TimingPower Cycle Time Power Cycle TimingSerial Port TIMING, Mode BYTE-WIDE ADDRESS/DATA BUS Timing Parameter Symbol MIN MAX Units BYTE-WIDE BUS TimingAC CHARACTERISTICS, DMA AC CharacteristicsRPC Timing Mode DS5001FP PIN Mqfp PIN Mqfp Revision History
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