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PDF DS1977 Data sheet ( Hoja de datos )
| Número de pieza | DS1977 | |
| Descripción | 32KB EEPROM iButton | |
| Fabricantes | Dallas Semiconducotr | |
| Logotipo |  |
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General Description
The DS1977 is a 32Kbyte 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 via
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 trace-ability. The
durable stainless steel iButton package is highly
resistant to environmental hazards such as dirt and
shock. Accessories permit the DS1977 iButton to be
mounted on almost any object, including containers,
pallets and bags.
Applications
• Maintenance and Inspection of equipment
• Medical Information / Health
• Data Shuttle for Fleet Management and Vending
applications
Ordering Information
Part Temp Range
DS1977-F5 -40 to 85°C
Pin-Pkg
F5 iButton
DS1977
32KB EEPROM iButton
Features
• 32KB EEPROM memory
• Durable, stainless-steel iButton package
• Built-in multi-drop controller ensures
compatibility with other Dallas Semiconductor
1-Wire net products
• Unique factory lasered 64-bit registration
number assures error free device selection
and absolute part identity
• Supports Overdrive mode
• Operating range: 2.8V to 5.25V, -40 to +85°C
Pin Configuration
5.89
0.36
0.51
© 1993
YYWW REGISTERED RR
CxCx 21xx
15C000FBC52B
15C0010-WFBireC52B
16.25
17.35
IO
GND
F5 iButton
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Writing With Verification
To write data to the DS1977 iButton, the scratchpad has to be used as intermediate storage. First
the 1-Wire master issues the Write Scratchpad command to specify the desired target address,
followed by the data to be written to the scratchpad. Under certain conditions (see Write
Scratchpad command) the 1-Wire master will receive an inverted CRC16 of the command,
address and data at the end of the write scratchpad command sequence. Knowing this CRC
value, the 1-Wire master can compare it to the value it has calculated itself to decide if the
communication was successful and proceed to the Copy Scratchpad command. If the 1-Wire
master could not receive the CRC16, it has to send the Read Scratchpad command to read back
the scratchpad to verify data integrity. As preamble to the scratchpad data, the DS1977 iButton
repeats the target address TA1 and TA2 and sends the contents of the E/S register. If the PF flag
is set, data did not arrive correctly in the scratchpad or there was a loss of power since data was
last written to the scratchpad. The 1-Wire master does not need to continue reading; it can start a
new trial to write data to the scratchpad. Similarly, a set AA flag together with a cleared PF flag
indicates that the Write command was not recognized by the device. If everything went correctly,
both flags are cleared and the ending offset indicates the address of the last byte written to the
scratchpad. Now the 1-Wire master can continue reading and verifying every data byte. After the
1-Wire master has verified the data, it has to send the Copy Scratchpad command. This
command must be followed exactly by the data of the three address registers TA1, TA2 and E/S.
The 1-Wire master may obtain the contents of these registers by reading the scratchpad or derive
it from the target address and the amount of data to be written. As soon as the DS1977 iButton
has received these bytes correctly and the 1-Wire master has provided an acceptable password,
the DS1977 will copy the scratchpad data to the requested location beginning at the target
address.
Memory and Control Functions
The DS1977 supports the following functions:
• Write Scratchpad (iButton version only)
• Read Scratchpad (iButton version only)
• Copy Scratchpad with Password (iButton version only)
• Read Memory with Password (iButton version only)
• Verify Password (iButton version only)
The following pages provide a short discussion of these functions. For the detailed flow charts
refer to Figure ??. The TA1, TA2, E/S logic is described in section Address Registers and
Transfer Status.
Write Scratchpad Command [0Fh]
After issuing the write scratchpad command, the 1-Wire master must first provide the 2-byte
target address, followed by the data to be written to the scratchpad. The data will be written to the
scratchpad starting at the byte offset (T5:T0). The ending offset (E5: E0) will be the byte offset at
which the 1-Wire master stops writing data. Only full data bytes are accepted. If the last data byte
is incomplete its content will be ignored and the partial byte flag PF will be set. When writing to a
password address, internal circuitry of the chip will force the 3 least significant address bits to 0.
Only full 8-byte passwords are accepted. The ending offset will be 07 or 0F, depending on the
password(s) to be changed.
When executing the Write Scratchpad command the CRC generator inside the DS1977 iButton
(see Figure ??) calculates a CRC over the entire data stream, starting at the command code and
ending at the last data byte sent by the 1-Wire master. This CRC is generated using the CRC16
polynomial by first clearing the CRC generator and then shifting in the command code (0FH) of
the Write Scratchpad command, the Target Addresses TA1 and TA2 as supplied by the 1-Wire
master and all the data bytes. The 1-Wire master may end the Write Scratchpad command at any
time. However, if the ending offset is 3Fh, the 1-Wire master may send 16 read time slots and will
receive the CRC generated by the DS1977 iButton.
Page 5
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Figure 5-4. Memory Function Flow Chart, Part 4
C3h
Verify
Password
N
Y
Master TX
TA1 (T7:T0), TA2 (T15:T8)
Address of
Password?
Y
N
DS1977 sets Memory
Address = (T15:T3, 0, 0, 0)
Master TX
Password to verify
Master Activates
Strong Pull-up
Password
Match?
Y
Master RX
AAh byte
N
Master
TX Reset?
Y
N
Master RX
FFh byte
Master
TX Reset?
Y
N
Page 11
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1/31/03
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet DS1977.PDF ] | |
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