19-4890; 11/09
DS1977
Password-Protected
32KB EEPROM iButton
www.maxim-ic.com
iButton DESCRIPTION
The DS1977 is a 32KB EEPROM in a rugged,
iButton
®
enclosure. Access to the memory can be
password-protected with different passwords for
read-only and full access. Data is transferred serially
through the 1-Wire
®
protocol, which requires only a
single data lead and a ground return. Every DS1977
is factory lasered with a guaranteed unique 64-bit
registration number that allows for absolute
traceability. The durable stainless-steel iButton
package is highly resistant to environmental hazards
such as dirt, moisture, and shock. Accessories permit
the DS1977 iButton to be mounted on almost any
object, including containers, pallets, and bags.
SPECIAL FEATURES
32KB EEPROM Organized as Pages of 64 Bytes
Each
Optional Password Protection with Different 64-
Bit Passwords for Read and Full Access
Communicates to Host with a Single Digital
Signal at Up to 15.3kbps at Standard Speed or
Up to 125kbps in Overdrive Mode Using 1-Wire
Protocol
Operating Range: 2.8V to 5.25V, -40C to +85C
Minimum 100k Write Cycles Endurance
15kV Built-in ESD Protection
Unique Factory-Lasered 64-Bit Registration
Number Assures Error-Free Device Selection
and Absolute Traceability Because No Two Parts
are Alike
Built-In Multidrop Controller for 1-Wire Net
Chip-Based Data Carrier Stores Digital
Identification and Information, Armored in a
Durable Stainless-Steel Case
Data can be Accessed While Affixed to Object
Button Shape is Self-Aligning with Cup-Shaped
Probes
Easily Affixed with Self-Stick Adhesive Backing,
Latched by its Flange, or Locked with a Ring
Pressed onto its Rim
Presence Detector Acknowledges when Reader
First Applies Voltage
COMMON iButton FEATURES
APPLICATIONS
Maintenance/Inspection Data Storage
Medical Data Carrier
Health Data Carrier
Audit Data Storage and Carrier
F5 MicroCAN
5.89
0.51
16.25
000000FBC52B
1-Wire
FC
37
17.35
ORDERING INFORMATION
PART
DS1977-F5#
TEMP RANGE
-40C to +85C
PACKAGE
F5 iButton
#Denotes an RoHS-compliant device that may include lead(Pb)
that is exempt under the RoHS requirements.
IO
GND
EXAMPLES OF ACCESSORIES
PART
DS9096P
DS9101
DS9093RA
DS9093A
DS9092
DESCRIPTION
Self-Stick Adhesive Pad
Multipurpose Clip
Mounting Lock Ring
Snap-In Fob
iButton Probe
All dimensions are shown in millimeters.
iButton and 1-Wire are registered trademarks of Maxim
Integrated Products, Inc.
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DS1977
PHYSICAL SPECIFICATION
Size
Weight DS1977
See mechanical drawing
Ca. 3.3g
ABSOLUTE MAXIMUM RATINGS
I/O Voltage to GND
I/O Sink Current
Junction Temperature
Storage Temperature Range
-0.3V, +5.5V
20mA
+150°C
-40°C to +85°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is
not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device.
ELECTRICAL CHARACTERISTICS
(V
PUP
= 2.8V to 5.25V, T
A
= -40°C to +85°C.)
PARAMETER
SYMBOL
CONDITIONS
I/O Pin General Data
1-Wire Pullup
(Notes 1, 2)
R
PUP
Resistance
Input Capacitance
C
IO
(Note 3)
Input Load Current
I
L
I/O pin at V
PUP
High-to-Low Switching
(Notes 4, 5)
V
TL
Threshold
Input Low Voltage
V
IL
(Notes 1, 6)
Low-to-High Switching
(Notes 4, 7)
V
TH
Threshold
Switching Hysteresis
V
HY
(Note 8)
Output-Low Voltage at
(Note 9)
V
OL
4mA
Standard speed, R
PUP
= 2.2k
(Note 1)
Overdrive speed, R
PUP
= 2.2k
Recovery Time
t
REC
(Note 1)
Overdrive speed, directly prior
to reset pulse; R
PUP
= 2.2k
(Note 1)
Rising-Edge Hold-off
Standard speed (Note 10)
t
REH
Time
Overdrive speed (Note 10)
Standard speed (Note 1)
Timeslot Duration
t
SLOT
Overdrive speed (Note 1)
I/O Pin, 1-Wire Reset, Presence Detect Cycle
Standard speed (Note 1)
Reset Low Time
t
RSTL
Overdrive Speed (Note 1)
Presence Detect High
Standard speed (Note 11)
t
PDH
Time
Overdrive speed (Note 11)
Standard speed, V
PUP
> 4.5V
(Note 12)
Presence Detect Fall
t
FPD
Time
Standard speed (Note 12)
Overdrive speed (Note 12)
Presence Detect Low
Standard speed
t
PDL
Time
Overdrive speed
MIN
0.6
1
0.5
0.7
0.15
TYP
MAX
2.2
5
10
3.2
0.30
3.4
N/A
0.4
5
2
5
0.5
0.5
65
8
480
48
15
2.5
1.5
1.5
0.15
60
8
5
2
µs
µs
640
80
60
6.5
5
8
1
240
24
µs
µs
µs
µs
µs
UNITS
k
nF
µA
V
V
V
V
V
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DS1977
PARAMETER
Presence Detect
Sample Time
I/O Pin, 1-Wire Write
Write-0 Low Time
Write-1 Low Time
I/O Pin, 1-Wire Read
Read Low Time
t
RL
Standard speed (Notes 1, 14)
Overdrive speed (Notes 1, 14)
Standard speed,
V
PUP
> 4.5V (Notes 1, 14)
Standard speed (Notes 1, 14)
Overdrive speed (Notes 1, 14)
(Note 1)
(Note 1)
(Note 1)
5
1
t
RL
+
t
RL
+
t
RL
+
2.64
22.46
0.62
7
100k
10
15 -
2-
20
15
2
µs
µs
t
W0L
t
W1L
Standard speed (Notes 1, 13)
Overdrive speed (Notes 1, 13)
Standard speed (Notes 1, 13)
Overdrive speed (Notes 1, 13)
60
6
5
1
120
16
15
2
µs
µs
SYMBOL
t
MSP
CONDITIONS
Standard speed, V
PUP
> 4.5V
(Note 1)
Standard speed (Note 1)
Overdrive speed (Note 1)
MIN
65
68
7.5
TYP
MAX
75
75
10.5
µs
UNITS
Read Sample Time
I/O Pin, Strong Pullup
Strong Pullup Read
Strong Pullup Write
Strong Pullup password
verification
EEPROM
Programming Current
Write/Erase Cycles
Data Retention
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
Note 14:
t
MSR
t
SPUR
t
SPUW
t
SPUV
I
LPROG
N
CYCLE
t
RET
ms
ms
ms
mA
—
years
System requirement.
Maximum allowable pullup resistance is a function of the number of 1-Wire devices in the system and 1-Wire recovery times. The
specified value here applies to systems with only one device and with the minimum 1-Wire recovery times. For more heavily loaded
systems, an active pullup such as that found in the DS2480B may be required.
Capacitance on the data pin could be 5nF when power is first applied.
V
TL
and V
TH
are functions of the internal supply voltage, which is a function of V
PUP
and the 1-Wire recovery times. The V
TH
and V
TL
maximum specifications are valid at V
PUPMAX
(5.25V). In any case, V
TL
< V
TH
< V
PUP
.
Voltage below which, during a falling edge on I/O, a logic '0' is detected.
The voltage on I/O needs to be less or equal to V
ILMAX
whenever the master drives the line low.
Voltage above which, during a rising edge on I/O, a logic '1' is detected.
After V
TH
is crossed during a rising edge on I/O, the voltage on I/O has to drop by V
HY
to be detected as logic '0'.
The I-V characteristic is linear for voltages less than 1V.
The earliest recognition of a negative edge is possible at t
REH
after V
TH
has been reached before.
Highlighted numbers are NOT in compliance with the published iButton standards. See comparison table below.
Interval during the negative edge on I/O at the beginning of a Presence Detect pulse between the time at which the voltage is 90%
of V
PUP
and the time at which the voltage is 10% of V
PUP
.
in Figure 11 represents the time required for the pullup circuitry to pull the voltage on I/O up from V
IL
to V
TH
. The actual maximum
duration for the master to pull the line low is t
W1LMAX
+ t
F
-
and t
W0LMAX
+ t
F
-
respectively.
in Figure 11 represents the time required for the pullup circuitry to pull the voltage on I/O up from V
IL
to the input-high threshold of
the bus master. The actual maximum duration for the master to pull the line low is t
RLMAX
+ t
F
.
Parameter
Name
t
SLOT
(incl. t
REC
)
t
RSTL
t
PDH
t
PDL
t
W0L
Standard Values
Standard Speed
Overdrive Speed
min
max
min
max
61µs
(undef.)
7µs
(undef.)
480µs
(undef.)
48µs
80µs
15µs
60µs
2µs
6µs
60µs
240µs
8µs
24µs
60µs
120µs
6µs
16µs
DS1977 Values
Standard Speed
Overdrive Speed
min
max
min
max
1)
1)
65µs
(undef.)
8µs
(undef.)
480µs
640µs
48µs
80µs
15µs
60µs
2.5µs
6.5µs
60µs
240µs
8µs
24µs
60µs
120µs
6µs
16µs
1) Intentional change, longer recovery time requirement due to modified 1-Wire front end.
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DS1977
APPLICATION
The DS1977 is an ideal device to store maintenance and inspection data of equipment or medical- and health-
related data in digitally readable format. Due to its small size and rugged enclosure the device can be carried with a
keyring to provide critical data in case of an emergency. The DS1977 can also serve as data shuttle to transport
fleet management and vending machine data to an access point for upload into a remote server for further
processing. Software for communication with the DS1977 is available for free download from the iButton website.
OVERVIEW
The block diagram in Figure 1 shows the relationships between the major control and memory sections of the
DS1977. The device has four main data components: 1) 64-bit lasered ROM, 2) 512-bit scratchpad and buffer, 3)
32KB EEPROM, and 4) two password buffers. The passwords can only be written and verified, but never be read.
The hierarchical structure of the 1-Wire protocol is shown in Figure 2. The bus master must first provide one of the
seven ROM function commands: 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM, 5) Overdrive-Skip
ROM, 6) Overdrive-Match ROM or 7) Resume. Upon completion of an Overdrive ROM command byte executed at
standard speed, the device will enter Overdrive mode, where all subsequent communication occurs at a higher
speed. The protocol required for these ROM function commands is described in Figure 9. After a ROM function
command is successfully executed, the memory and control functions become accessible and the master may
provide any one of the six available commands. The protocol for these memory and control function commands is
described in Figure 7. All data is read and written least significant bit first.
Figure 1.
DS1977 BLOCK DIAGRAM
I/O
POWER
CONTROL
ROM FUNCTION
CONTROL
64-BIT
LASERED ROM
CRC16
GENERATOR
MEMORY
FUNCTION
CONTROL
64-BYTE
SCRATCHPAD
AND BUFFER
MEMORY
ACCESS
SECURITY
CONTROL
32KB
EEPROM
4 of 29
DS1977
Figure 2. HIERARCHICAL STRUCTURE FOR 1-WIRE PROTOCOL
BUS
MASTER
1-Wire NET
OTHER
DEVICES
DS1977
COMMAND
LEVEL:
AVAILABLE
COMMANDS:
READ ROM
MATCH ROM
SEARCH ROM
SKIP ROM
RESUME
OVERDRIVE SKIP
OVERDRIVE MATCH
WRITE SCRATCHPAD
READ SCRATCHPAD
COPY SCRATCHPAD
W/PW
READ MEMORY W/PW
VERIFY PASSWORD
READ VERSION
DATA FIELD
AFFECTED:
64-BIT ROM, RC-FLAG
64-BIT ROM, RC-FLAG
64-BIT ROM, RC-FLAG
RC-FLAG
RC-FLAG
RC-FLAG, OD-FLAG
64-BIT ROM, RC-FLAG, OD-FLAG
64-BYTE SCRATCHPAD
64-BYTE SCRATCHPAD
DATA MEMORY, PASSWORDS,
PASSWORD ENABLE BYTE
DATA MEMORY, PASSWORDS,
PASSWORD ENABLE BYTE
PASSWORDS
VERSION REGISTER
1-Wire ROM FUNCTION
COMMANDS
DS1977-SPECIFIC
MEMORY FUNCTION
COMMANDS
64-BIT LASERED ROM
Each DS1977 contains a unique ROM code that is 64 bits long. The first 8 bits are a 1-Wire family code. The next
48 bits are a unique serial number. The last 8 bits are a CRC of the first 56 bits. See Figure 3 for details. The 1-
Wire CRC is generated using a polynomial generator consisting of a Shift and XOR gates as shown in Figure 4.
The polynomial is X
8
+ X
5
+ X
4
+ 1. Additional information about the 1-Wire Cyclic Redundancy Check is available
in Application Note 27 and in the
Book of DS19xx iButton Standards.
The Shift register bits are initialized to 0. Then starting with the least significant bit of the family code, one bit at a
time is shifted in. After the 8
th
bit of the family code has been entered, then the serial number is entered. After the
48
th
bit of the serial number has been entered, the Shift register contains the CRC value. Shifting in the 8 bits of
CRC returns the Shift register to all 0s.
Figure 3. 64-BIT LASERED ROM
MSB
8-BIT
CRC CODE
MSB
LSB
MSB
48-BIT SERIAL NUMBER
LSB
LSB
8-BIT FAMILY
CODE (37h)
MSB
LSB
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EEWORLD
