ds2251 Maxim Integrated Products, Inc., ds2251 Datasheet - Page 2

• Manufacturer Part Number: ds2251
• Description: 128k Soft Microcontroller Module
• Manufacturer: Maxim Integrated Products, Inc.

The DS2251T provides the benefits of NV RAM without using I/O resources. Between 32 kbytes and 128
kbytes of onboard NV RAM are available. A non-multiplexed Byte-wide address and data bus is used for
memory access. This bus, which is available at the connector, can perform all memory access and also
provide decoded chip enables for off-board memory mapped peripherals. This leaves the 32 I/O port pins
free for application use.
The DS2251T provides high-reliability operation in portable 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 maintained 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 NV RAM, validates it, then becomes transparent to the user. Software is
stored in onboard 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
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.
DS2251T-32-16
DS2251T-64-16
DS2251T-128-16
PART NUMBER
RAM SIZE
128 kbytes
32 kbytes
64 kbytes
2 of 20
MAX CRYSTAL
16 MHz
16 MHz
16 MHz
SPEED
TIMEKEEPING?
Yes
Yes
Yes
DS2251T