DS1204V
DS1204V
Electronic Key
FEATURES
• Cannot be deciphered by reverse engineering
• Partitioned memory thwarts pirating
• User-insertable packaging allows personal posses-
sion
• Exclusive blank keys on request
• Appropriate identification can be made with a 64-bit
reprogrammable memory
• Unreadable 64-bit security match code virtually pre-
vents deciphering by exhaustive search with over
1019 possibilities
• 128 bits of secure read/write memory create addition-
al barriers by permitting data changes as often as
needed
• Rapid erasure of identification security match code
and secure read/write memory can occur if tampering
is detected
• Low-power CMOS circuitry
• Four million bps data rate
• Durable and rugged
• Applications include software authorization, gray
market software protection, proprietary data, financial
transactions, secure personnel areas, and system ac-
cess control
DESCRIPTION
The DS1204V Electronic Key is a miniature security
system that stores 64 bits of user-definable identifica-
tion code and a 64-bit security match code that protects
128 bits of read/write nonvolatile memory. The 64-bit
identification code and the security match code are pro-
grammed into the key via a special program mode oper-
ation. After programming, the key follows a procedure
with a serial format to retrieve or update data. Interface
cost to a microprocessor is minimized by on-chip circuit-
ry that permits data transfer with only three signals:
Clock (CLK), Reset (RST), and Data Input/Output (DQ).
PIN ASSIGNMENT
DALLAS
DS1204V
ELECTRONIC KEY
SIDE
1
5
BOTTOM: PIN VIEW
1.0 IN
See Mech. Drawings
Section
PIN DESCRIPTION
Pin 1 - VCC
Pin 2 - RST
Pin 3 - DQ
Pin 4 - CLK
Pin 5 - GND
+5 Volts
Reset
Data Input/Output
Clock
Ground
Low pin count and a guided entry for mating receptacle
overcome mechanical problems normally encountered
with conventional integrated circuit packaging, making
the device transportable and user-insertable.
OPERATION – NORMAL MODE
The Electronic Key has two modes of operation: normal
and program. The block diagram (see Figure 1) illus-
trates the main elements of the key when used in the
normal mode. To initiate data transfer with the key, RST
is taken high and 24 bits are loaded into the command
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