DS2251T(1995) 查看數據表（PDF） - Dallas Semiconductor -> Maxim Integrated

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DS2251T
(Rev.:1995)

128K Soft Microcontroller Module

Dallas Semiconductor -> Maxim Integrated 

DS2251T

DS2251T MEMORY MAP WITH (PES=1) Figure 4

FFFFh

PROGRAM MEMORY

ÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌ C000h

ÌÌÌÌÌÌ PARTITION

ÎÎÌÎÎÌÎÎÌÎÎÌÎÎÌÎÎÌ 8000h

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ 4000h

NVRAM

PROGRAM

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ 0000h

ÌÌÌÌ

NOT ACCESSIBLE

DATA MEMORY (MOVX)

64K

PE4

48K

ÌÌÌÌÌÌÌÌÌÌÌÌPE3ÌÌÌÌÌÌÌÌ

32K

16K

REAL–TIME

CLOCK

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 ref-

erence in determining the switch points. These are

called VPFW, VCCMIN, and VLI respectively. When VCC

drops below VPFW, the DS2251T will perform an inter-

rupt vector to location 2Bh if the power fail warning was

enabled. Full processor operation continues regard-

less. 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 inac-

tive (logic 1) state. The VRST signal will be driven to a 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.

121395 8/19

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