A Non-Disclosure Agreement (NDA) is required for full disclosure of details. Contact factory for more information.
DS5250
High-Speed Secure Microcontroller
www.maxim-ic.com
GENERAL DESCRIPTION
The DS5250 is a highly secure, 4 clocks-per-machine
cycle, 100% 8051-instruction-set-compatible
microprocessor in the Secure Microcontroller family
from Dallas Semiconductor. It was designed to be the
cryptographic engine of PIN pads, financial terminals,
and any other application in which data security is
paramount. A key feature of the device is that it
encrypts its program memory with a hardware-based
single or triple (3) DES (data encryption standard)
algorithm, making it nearly impossible to extract
information. Another DES (3DES) hardware block is
available to the user for encrypting arbitrary information
in data memory space. This makes the device ideal for
storage and transmission of passwords, personal
identification numbers, encryption keys, and other highly
confidential information.
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Advanced Features
CRC-16/32 Generator
5kB Internal SRAM (Optional 1kB Stack)
Single or 3DES Engine
Partitionable Memory Segments Variable from 4kB to
256kB
High-Speed Architecture
4 Clocks-per-Machine Cycle
DC-to-25MHz Operation
Single-Cycle Instruction in 160ns
Dual Data Pointers can Increment or Decrement
Independently
Automatic Data Pointer Selection Available
Programmable Speed MOVX Instructions
1kB On-Chip Instruction Cache
High-Reliability Operation
Power-Fail/Overvoltage Reset
Early-Warning Power-Fail Interrupt
Watchdog Timer
Nonvolatile Functions
On-Chip Real-Time Clock with Alarm Interrupt
2kB Battery-Backed Internal SRAM
Security Features
Designed to Meet the Physical Security Requirements
of FIPS-140 and Common Criteria Certifications
Program Memory Integrity Checking
Executes Single/3DES-Encrypted Programs to
Prevent Observation
Separate Program/Data Cryptograph
Two Self-Destruct Inputs
4096-Bit Modulo-Arithmetic Accelerator (MAA) for PKI
Operations
Built-In Sensors Detect Attack and Cause Security
Response
Programmable Attack Countermeasures
Secure Bootstrap Loader
True Random-Number Generator (RNG)
Unique ID Number in Every Device
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APPLICATIONS
PIN Pads
Financial Terminals
Applications that Require Data Security
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ORDERING INFORMATION
PART
DS5250F-825
DS5250F-125
DS5250F-8N5
DS5250F-1N5
TEMP RANGE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
MAX
CLOCK
SPEED
(MHz)
25
25
25
25
PIN-PACKAGE
80 Plastic MQFP
100 Plastic MQFP
80 Plastic MQFP
100 Plastic MQFP
Pin Configurations appear on page 2.
FEATURES
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Drop-In Upgrade to the Dallas DS5240
Feature-Rich, 8051-Compatible, Highly Secure
Microcontroller
Accesses Up to 4MB Program and 4MB Data Memory
(All Nonvolatile)
In-System Programmable through Serial Port
In-Application Programmable through User Software;
Allows Self-Modification of Program/Data Memory
Four 8-Bit Ports/One 6-Bit Port
Three 16-Bit Timer/Counters
256 Bytes of Scratchpad RAM
Note:
Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about DS5250 errata, contact the factory.
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REV: 071803
A Non-Disclosure Agreement (NDA) is required for full disclosure of details. Contact factory for more information.
DS5250 High-Speed Secure Microcontroller
DETAILED DESCRIPTION
The DS5250 has a user-selectable, program memory integrity-checking feature that triggers a tamper response if
the decrypted program memory does not match a precalculated checksum, indicating a possible attack. In addition,
all encryption keys for encrypted memory are stored in internal battery-backed SRAM so they can be erased
instantaneously in the event tamper activity is detected. The battery-backed memory architecture subjects critical
application data and encryption keys stored internally to instantaneous zeroization, as defined in Federal
Information Processing Standard (FIPS) 140-1 as a tamper response. Additionally, power is removed from external
memory, and all data and address lines are collapsed as an additional response to tamper detection.
The DS5250 incorporates the most sophisticated security features available in any microprocessor. The security
features resist multiple levels of threat, including observation, analysis, and physical attack. Attempts to discover
the device’s encryption keys result in their erasure, rendering useless the encrypted external memory. Such
measures require a massive effort to acquire any information about the memory contents. Sophisticated internal
sensors monitor various environmental parameters, and trigger a tamper response if they deviate from acceptable
levels. A microprobe shield covers the top of the microcontroller die and deters tampering by triggering a
destructive reset if it is breached. Other security measures implement defenses against known direct and side-
channel attacks. Specific security-related hardware includes a 4096-bit MAA for public key infrastructure (PKI)
calculations, a random-number generator, a CRC-16/32 generator, and a user-available DES (or 3DES) engine.
In addition to the internal sensors, two external self-destruct input (SDI) pins allow the designer to trigger a tamper
response based on user-defined external stimuli. One SDI input controls destruction of program memory, external
data memory, cache memory, key registers, and all the internal 5kB RAM. The second SDI functions as an
interrupt, allowing the application software to appropriately respond to a detected attack. Other security methods
include optional timed-access-write restrictions to the parallel I/O port pins, making certain attack practices
ineffective.
Program loading is accomplished using a secure ROM-based serial port bootloader. The battery-backed nature of
the DS5250, combined with an internal ROM-based bootloader, allows frequent modification of secure information,
either program or data, through a secure loading mechanism. An optional challenge-response protection of access
to the bootstrap-ROM loader ensures that only trusted agents can load programs into the device. Once the
challenge response has been successfully completed, communications between the host system and the
microcontroller are conducted in a 3DES cipher-block-chained data stream to prevent communication interception.
Alternatively, a user can create a custom bootloader using the microcontroller’s encryption tools.
PIN CONFIGURATIONS
TOP VIEW
80
81
51
50
64
41
Dallas
Semiconductor
65
DS5250
Dallas
Semiconductor
40
DS5250
80
25
100
1
30
31
1
24
MQFP
MQFP
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