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PDF DS1205S Data sheet ( Hoja de datos )
| Número de pieza | DS1205S | |
| Descripción | MultiKey Chip | |
| Fabricantes | Dallas Semiconducotr | |
| Logotipo |  |
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DS1205S
DS1205S
MultiKey Chip
FEATURES
• Three secure read/write data partitions of 384 bits
each
• One non-secure read/write data partition of 512 bits
• Secure data cannot be deciphered by reverse engi-
neering
• Guaranteed unique, 48-bit, laser etched serial
number
• 64-bit password and I.D. fields provide positive identi-
fication and security for each secure data partition
• Maximum data transfer rate of 2 million bits/second
• Low-power CMOS circuitry
• Access via 3-wire or 1-wire interface
• Applications include proprietary data, financial trans-
actions, secure personnel areas, and systems ac-
cess control
PIN ASSIGNMENT
VCCI
NC
RST
DQ
NC
CLK
NC
GND
1
2
3
4
5
6
7
8
VCCO
16
15 NC
14 I/O
13 GND
12 NC
11 DQOE
10 NC
9 BAT
DS1205S 16-Pin SOIC (300 mil)
See Mech. Drawings
Section
PIN DESCRIPTION
VCCI
RST
– +5V Supply (Battery Backup Mode)
– Reset (3-Wire)
DQ – Data (3-Wire)
CLK – Clock (3-Wire)
GND
– Ground
BAT – Battery (+) (Battery Backup Mode)
DQOE
– Data Available (3-Wire)
I/O – Data I/O (1-Wire)
VCCO
– Battery (+) (Battery Powered Mode)
DESCRIPTION
The DS1205S MultiKey Chip is an enhanced version of
the DS1204U Electronic Key which has both a standard
3-wire interface (data, clock, and reset) and a 1-wire in-
terface. The DS1205S MultiKey has three secure read/
write subkeys which are each 384 bits in length. In addi-
tion, there is a 512-bit read/write scratchpad which can
be used as a non-secure data area or as a holding regis-
ter for data transfer to one of the three subkeys. Each
subkey within the part is uniquely addressable on byte
boundaries.
OPERATING MODES
There are two modes of operation for powering the
DS1205S MultiKey Chip. In the Normal Mode (Battery
Backup), VCC power is supplied to the part on the VCCI
pin, while the battery backup source is applied to the
BAT pin. In this mode of operation, the chip supply is
switched internally between VCCI and BAT (depending
on which is higher) and this level is presented internally
to the VCCO pin. In the Battery Operate Mode, the bat-
tery supply is connected directly to the VCCO pin while
the VCCI and BAT pins are grounded.
021798 1/17
1 page  
SET SECURITY MATCH Figure 5
WRITE SET PASSWORD
IN COMMAND WORD
(SPECIFY WHICH
SECURE PARTITION)
SET SECURE DATA Figure 6
WRITE SET SECURE DATA
IN COMMAND WORD (SPECIFY
WHICH SECURE PARTITION AND
STARTING BYTE ADDRESS)
DS1205S
READ I.D. FIELD FROM
SECURE PARTITION
(64 BITS)
WRITE 64 BITS OF DATA
TO DS1205
(OLD I.D.)
READ I.D. FIELD FROM
SECURE PARTITION
(64 BITS)
WRITE 64 BITS OF DATA
TO DS1205
IS DATA = I.D?
NO
YES
ERASE I.D. AND PASSWORD
FIELD, SECURE DATA
FIELD FOR SELECTED
SECURE PARTITION.
TERMINATE
TRANSACTION
WRITE 64 BITS OF DATA
FOR NEW I.D. FIELD DATA
IS DATA =
PASSWORD?
NO
TERMINATE
TRANSACTION
YES
WRITE DATA TO SECURE
DATA FIELD (STARTING
ADDRESS SPECIFIED IN
COMMAND WORD)*
*Data is written to the DS1205S beginning
at the specified address and continuing
until either Bit 511 is written or the RST
line is brought low.
WRITE 64 BITS OF DATA
FOR NEW PASSWORD
FIELD DATA
TERMINATE TRANSACTION
TERMINATE
TRANSACTION
021798 5/17
5 Page 
RESET/PRESENCE DETECT SEQUENCE Figure 17
tSYC
RESET PULSE
DRIVEN LOW
BY HOST
IDLE
STATE
DS1205S
FIRST BIT OF 1–WIRE
PROTOCOL
PRESENCE DETECT
DRIVEN BY 1–WIRE
DEVICE
tRSTL
tPDH
tPDL
tRSTH
1-Wire I/O Commands - Once the bus master has de-
tected a presence, it can issue one of the four different
1-wire I/O commands. These commands deal with the
laser-etched ROM code which has the following format.
Type ID
8 bits
Unique Serial Number CRC
48 bits
8 bits
All 1-wire commands are eight bits long. A list of these
commands are as follows:
CCh Pass Thru Mode
This command saves time by allowing direct ac-
cess to the DS1205S without identifying it by
ROM ID number. This command can only be used
when there is a single slave on the bus. If more
than one device is present, there will be bus con-
tention.
33h Read ROM Data
This command allows the bus master to read the
DS1205S’s unique 48-bit ID number and CRC.
This command can only be used if there is a
single DS1205S on the bus. If more than one is
present, there will be bus contention.
55H Match ROM Data
This mode allows the bus master to single out a
specific DS1205S on a multidrop bus. The bus
master selects the specific slave by the ROM ID
number for the transaction. This command can be
used with a single or multiple device on the bus.
F0h Search ROM Data
When a system is initially brought up, the bus
master might not know the number or types of de-
vices on the bus. By invoking the Search ROM
Data command the bus master can, by process of
elimination, find the ID numbers of all the devices
on the bus. Once this is known, the bus master
can then go back and read the device type that
corresponds to each ID number.
The ROM search process is the repetition of a simple
3-step routine: read a bit, read the complement of the
same bit, then write the desired value of that bit. The bus
master performs this simple 3-step routine on each bit of
the ROM. After one complete pass, the bus master
knows the contents of the ROM in one device. The bus
is reset and the process is repeated again, selecting a
different set of bit values. The bus master controls the
search according to what values are written as select
bits.
The following example of the ROM search process as-
sumes four different devices are connected to the same
1-wire bus. The ROM data of the four devices is as
shown:
ROM1
ROM2
ROM3
ROM4
00110101...
10101010...
11110101...
00010001...
The search process is as follows:
1. The bus master begins by resetting all devices pres-
ent on the 1-wire bus. After this, the bus master will
attempt to read the family code, serial number, and
CRC value for the part.
2. The bus master will then issue the Search ROM
Data command on the 1-wire bus.
3. The bus master performs two reads and receives
two 0 bits. This indicates that both 1 bits and 0 bits
exist as the first bit of the devices on the bus.
021798 11/17
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