DS2251T

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mapped peripherals. This leaves the 32 I/O port pins

free for application use.

The DS2251T provides high–reliability operation in por-

table systems or systems with unreliable power. These

features include the ability to save the operating state,

Power–fail Reset, Power–fail Interrupt, and Watchdog

Timer. All nonvolatile memory and resources are main-

tained for over 10 years at room temperature in the

absence of power.

A user loads programs into the DS2251T via its on–chip

Serial Bootstrap Loader. This function supervises the

loading of software into NVRAM, validates it, then

becomes transparent to the user. Software is stored in

on–board CMOS SRAM. Using its internal Partitioning,

the DS2251T can divide a common RAM into user

selectable program and data segments. This Partition

can be selected at program loading time, but can be

modified anytime later. The microprocessor will decode

memory access to the SRAM, access memory via its

Byte–wide bus and write–protect the memory portion

designated as program (ROM).

ORDERING INFORMATION

PART NUMBER

RAM SIZE

MAX CRYSTAL SPEED

TIMEKEEPING?

DS2251T–32–16

32K bytes

16 MHz

Yes

DS2251T–64–16

64K bytes

16 MHz

Yes

DS2251T–128–16

128K bytes

16 MHz

Yes

Operating information is contained in the User’s Guide section of the Secure Microcontroller Data Book. This data

sheet provides ordering information, pinout, and electrical specifications.