DS1996 Datasheet by Maxim Integrated

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maxim Integratedw DS1996 64Kb Memory iButton DATA \ GROUND ORDERING INFORMATION TEMP PIN- RANGE PACKAGE Wir OF A 1 Self Mu M S 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com. 19-4896; Rev 8/09
AVAILABLE
Functional Diagrams
Pin Configurations appear at end of data sheet.
Functional Diagrams continued at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
SPECIAL FEATURES
65,536 bits of read/write nonvolatile memory
Overdrive mode boosts communication
speed to 142 kbits per second
256-bit scratchpad ensures integrity of data
transfer
Memory partitioned into 256-bit pages for
packetizing data
Data integrity assured with strict read/write
protocols
Operating temperature range from -40°C to
+70°C
Over 10 years of data retention
F5 MICROCAN
DATA
GROUND
0.51
5.89
16.25
17.35
000000FBC52B
1-Wire
All dimensions are shown in millimeters
COMMON iButton FEATURES
Unique, factory-lasered and tested 64-bit
registration number (8-bit family code + 48-
bit serial number 8-bit CRC tester) assures
absolute traceability because no two parts are
alike
Multidrop controller for MicroLAN
Digital identification and information by
momentary contact
Chip-based data carrier compactly stores
information
Data can be accessed while affixed to object
Economically communicates to bus master
with a single digital signal at 16.3 kbits per
second
Standard 16 mm diameter and 1-Wire®
protocol ensure compatibility with iButton®
family
Button shape is self-aligning with cup-
shaped probes
Durable stainless steel case engraved with
registration number withstands harsh
environments
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
ORDERING INFORMATION
PART
TEMP
RANGE
PIN-
PACKAGE
DS1996L-F5+ -40°C to +70°C F5 MicroCan
+Denotes a lead(Pb)-free/RoHS-compliant package.
EXAMPLES OF ACCESSORIES
DS9096P Self-Stick Adhesive Pad
DS9101 Multi-Purpose Clip
DS9093RA Mounting Lock Ring
DS9093F Snap-In Fob
DS9092 iButton Probe
DS1996
64Kb Memory iButton
iButton and 1-Wire are registered trademarks of Maxim Integrated Products, Inc.
19-4896; Rev 8/09
IP istin i0 “mm m
DS1996
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iButton DESCRIPTION
The DS1996 Memory iButton is a rugged read/write data carrier that acts as a localized database that can
be easily accessed with minimal hardware. The nonvolatile memory offers a simple solution to storing
and retrieving vital information pertaining to the object to which the iButton is attached. Data is
transferred serially via the 1-Wire protocol which requires only a single data lead and a ground return.
The scratchpad is an additional page that acts as a buffer when writing to memory. Data is first written to
the scratchpad where it can be read back. After the data has been verified, a copy scratchpad command
will transfer the data to memory. This process ensures data integrity when modifying the memory. A
48-bit serial number is factory lasered into each DS1996 to provide a guaranteed unique identity which
allows for absolute traceability. The durable MicroCan package is highly resistant to environmental
hazards such as dirt, moisture, and shock. Its compact button-shaped profile is self-aligning with mating
receptacles, allowing the DS1996 to be easily used by human operators. Accessories permit the DS1996
to be mounted on almost any surface including plastic key fobs, photo-ID badges and printed circuit
boards. Applications include access control, work-in-progress tracking, electronic travelers, storage of
calibration constants, and debit tokens.
OVERVIEW
The block diagram in Figure 1 shows the relationships between the major control and memory sections of
the DS1996. The DS1996 has three main data components: 1) 64-bit lasered ROM, 2) 256-bit scratchpad
and 3) 65536-bit SRAM. The hierarchal structure of the 1-Wire protocol is shown in Figure 2. The bus
master must first provide one of the six ROM Function Commands, 1)Read ROM, 2) Match ROM, 3)
Search ROM, 4) Skip ROM, 5) Overdrive-Skip ROM or Overdrive-Match ROM. Upon completion of an
overdrive ROM command byte executed at regular 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 functions become accessible and the master may provide any one of the four memory function
commands. The protocol for these memory function commands is described in Figure 7. All data read and
written least significant bit first.
PARASITE POWER
The block diagram (Figure 1) shows the parasite-powered circuitry. This circuitrysteals” power
whenever the data line is high. The data line will provide sufficient power as long as the specified timing
and voltage requirements are met. The advantages of parasite power are two-fold: 1) by parasiting off this
input, battery power is not consumed for 1-Wire ROM function commands, and 2) if the battery is
exhausted for any reason, the ROM may still be read normally. The remaining circuitry of the DS1996 is
solely operated by battery energy.
64-BIT LASERED ROM
Each DS1996 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. (Figure 3.)
The 1-Wire CRC is generated using a polynomial generator consisting of a shift register and XOR gates
as shown in Figure 4. The polynomial is X8 + X5 + X4 + 1. Additional information about the Dallas 1-
Wire Cyclic Redundancy Check is available in the Book of DS19xx iButton Standards.
The shift register bits are initialized to zero. Then starting with the least significant bit of the family code,
1 bit at a time is shifted in. After the 8th bit of the family code has been entered, then the serial number is
entered. After the 48th bit of the serial number has been entered, the shift register contains the CRC
value. Shifting in the 8 bits of CRC should return the shift register to all zeros.
[ I LID I 1—me FUNCT‘ON 5”” ‘ CONTACT DATA OT CONTROL ‘— LASEEED \ 1 \ L _ A __________ J MEMORY <—» 255‘5”="" func-hon="" schatchpad="" control="" ‘—="" memory="" ‘="" 64kvb‘t="" —’="" sram="" (25mm="" pages)="" av="" uthium="">
DS1996
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DS1996 BLOCK DIAGRAM Figure 1
1-WIRE CRC GENERATOR Figure 4 lrWlRE BUS > OTHER DEVICES DS 1996 COMMAN AVAILABLE DATA FIELD LEVEL: COMMANDS: AFFECT D: IVWIRE ROM FUNCTION COMMANDS (SE1; FIGURE 9) DS 19967 SPECIFIC MORY FUNCTI COMMANDS (SEL‘ FIGURE 7) INPUT V (MSB) (LSB)
DS1996
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HIERARCHICAL STRUCTURE FOR 1-WIRE PROTOCOL Figure 2
64-BIT LASERED ROM Figure 3
8-Bit CRC Code 48-Bit Serial Number 8-Bit Family Code (0CH)
MSB LSB MSB LSB MSB LSB
1-WIRE CRC GENERATOR Figure 4
BUS
MASTER
OTHER
DEVICES
DS 1996
COMMAND AVAILABLE DATA FIELDS
LEVEL: COMMANDS: AFFECTED:
READ ROM 64-BIT ROM
MATCH ROM 64-BIT ROM
SEARCH ROM 64-BIT ROM
SKIP ROM N/A
OVERDRIVE SKIP ROM N/A
OVERDRIVE MATCH ROM 64-BIT ROM
WRITE SCRATCHPAD 256-BIT SCRATCHPAD
READ SCRATCHPAD 256-BIT SCRATCHPAD
COPY SCRATCHPAD 64K-BIT MEMORY
READ MEMORY 64K-BIT MEMORY
DS 1996- SPECIFIC
MEMORY FUNCTION
COMMANDS
(SEE FIGURE 7)
1-WIRE ROM FUNCTION
COMMANDS (SEE FIGURE 9)
1-WIRE BUS
TH V he DS be used as intermed ed target address, f he Read Scratchp atchpad data, 1h ister. Ifone of need to conti indicate hrec f ad. N send dr i
DS1996
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MEMORY
The memory map in Figure 5 shows a 32-byte page called the scratchpad and additional 32-byte pages
called memory. The DS1996 contains 256 pages which comprise the 65536-bit SRAM. The scratchpad is
an additional page that acts as a buffer when writing to memory.
ADDRESS REGISTERS AND TRANSFER STATUS
Because of the serial data transfer, the DS1996 employs three address registers, called TA1, TA2 and E/S
(Figure 6). Registers TA1 and TA2 must be loaded with the target address to which the data will be
written or from which data will be sent to the master upon a Read command. Register E/S acts like a byte
counter and Transfer Status register. It is used to verify data integrity with Write commands. Therefore,
the master only has read access to this register. The lower 5 bits of the E/S register indicate the address of
the last byte that has been written to the scratchpad. This address is called Ending Offset. Bit 5 of the E/S
register, called PF or ”partial byte flag,” is set if the number of data bits sent by the master is not an
integer multiple of 8. Bit 6, OF or ”Overflow,” is set if more bits are sent by the master than can be stored
in the scratchpad. Note that the lowest 5 bits of the target address also determine the address within the
scratchpad, where intermediate storage of data will begin. This address is called byte offset. If the target
address for a Write command is 13CH for example, then the scratchpad will store incoming data
beginning at the byte offset 1CH and will be full after only 4 bytes. The corresponding ending offset in
this example is 1FH. For best economy of speed and efficiency, the target address for writing should
point to the beginning of a new page, i.e., the byte offset will be 0. Thus the full 32-byte capacity of the
scratchpad is available, resulting also in the ending offset of 1FH. However, it is possible to write one or
several contiguous bytes somewhere within a page. The ending offset together with the Partial and
Overflow Flag is mainly a means to support the master checking the data integrity after a Write
command. The highest valued bit of the E/S register, called AA or Authorization Accepted, acts as a flag
to indicate that the data stored in the scratchpad has already been copied to the target memory address.
Writing data to the scratchpad clears this flag.
WRITING WITH VERIFICATION
To write data to the DS1996, the scratchpad has to be used as intermediate storage. First the master issues
the Write Scratchpad command to specify the desired target address, followed by the data to be written to
the scratchpad. In the next step, the master sends the Read Scratchpad command to read the scratchpad
and to verify data integrity. As preamble to the scratchpad data, the DS1996 sends the requested target
address TA1 and TA2 and the contents of the E/S register. If one of the flags OF or PF is set, data did not
arrive correctly in the scratchpad. The master does not need to continue reading; it can start a new trial to
write data to the scratchpad. Similarly, a set AA flag indicates that the Write command was not
recognized by the iButton. If everything went correctly, all three flags are cleared and the ending offset
indicates the address of the last byte written to the scratchpad. Now the master can continue verifying
every data bit. After the 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 as the
master has read them verifying the scratchpad. As soon as the iButton has received these bytes, it will
copy the data to the requested location beginning at the target address.
MEMORY FUNCTION COMMANDS
The “Memory Function Flow Chart” (Figure 7) describes the protocols necessary for accessing the
memory. An example follows the flowchart. The communication between master and DS1996 takes place
either at regular speed (default, OD=0) or at Overdrive Speed (OD=1). If not explicitly set into the
Overdrive Mode the DS1996 assumes regular speed.
32—byte Intermediale storage scratchpad STARTING ADDRESS moo“ 32—!)er final storage NV RAM 0020M 32-by\e final slorage NV HAM 64K-BIT NV HAM , , ‘ ‘ IFEGH 32—byte final storage NV RAM 8 REGISTERS Figure 6 7 6 5 4 3 2 I 0 TARGET ADDRESS (TA!) 17 76 15 1‘ T: T2 T‘ TO TARGET ADDRESS m2) “5 m m Tu Tu TID T9 TB END‘fifA’gfififis‘rEr/VS’: M 0F PF E4 E3 52 E1 E0 (READ ONLY) page 0 page 1 page 255
DS1996
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Write Scratchpad Command [0FH]
After issuing the write scratchpad command, the 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 (T4:T0). The ending offset (E4: E0) will be the byte offset at which the bus master has
stopped writing data.
Read Scratchpad Command [AAH]
This command is used to verify scratchpad data and target address. After issuing the read scratchpad
command, the master begins reading. The first 2 bytes will be the target address. The next byte will be the
ending offset/data status byte (E/S) followed by the scratchpad data beginning at the byte offset (T4: T0).
The master may read data until the end of the scratchpad after which the data read will be all logic 1’s.
DS1996 MEMORY MAP Figure 5
ADDRESS REGISTERS Figure 6
MORY FUNCTION FLOW CHART Figure 7 I) AAh READ SCHATCHFA . SCRATcHPA n MASTER TX MEMORY FROM ROM FUNCTION me CHART FUNCTION COMMAND (FISHEE 9) MASTER TX MASTER Rx MASTER Tx TAI (n-Top TM mm» TM (17:10) T T * MASTER Tx 1) TAT 17.Tn MASYER Tx 1, MASTER Rx 1. MASTER Tx “ ‘ ’ TA2(T15118) TA: (T‘s-Tap TA2 (TI5.TB) * T * * MASTER Tx 1) TAz mam Dsqgss sETs SCRATCHFAD ws'TER RX ENDING n MASTER Tx 0 OFFSET=(H-1o) AND oEEsET/DATA as BVTE * cLEARs (PF OF M) STATUS BYTE (E15) D5195} SETS * MEMon 1 Dsmss sETs ADDRESS=KTlfirTm MASTER TX DATA BVTE ‘ SCRATCHPAD To SCRATCHFAD OFFSET orFsET=mzvu1 ‘A MASTER Rx DATA 1) § RVTE FROM DSI996 sETs MASTER Rx DATA |) MEMon ADDREss (E4:Em=scRATcHPAD BYTE FROM OFFSET scRATcHPAD OFFSET 2] MASTER Tx V 2! RESET v MASTER TX INCREMENT N I*S'ET DST 99a COPIES MEMORY S‘Efiifé’m: SCRAYCNFAD ADDRESS mcREMENT DATA To MEWRV OF‘SE' SCRAYCHFAD N OFFSET scaATCHPAD OFFSET N smATcHPAD =an OFFSET :Illllb v 2) MASTER 1) Rx ‘I's MASTER 1) Rx ms |_ MASTER Tx I REEF N v To ROM EuNcTToNs FLOW CHART (FIGURE 9)
DS1996
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MEMORY FUNCTION FLOW CHART Figure 7
1) TO BE TRANSMITTED OR RECEIVED AT OVERDRIVE SPEED IF OD=1
2) RESET PULSE TO BE TRANSMITTED AT OVERDRIVE SPEED IF OD=1;
RESET PULSE TO BE TRANSMITTED AT REGULAR SPEED IF OD=0
OR IF THE DS1996 IS TO BE RESET FROM OVERDRIVE SPEED TO REGULAR SPEED
M E 1 MASTER MODE DATA (LSB FIRST) COMMENTS TX Reset Reset pulse (480-960 11s) RX Presence Presence pulse TX CCh Issue “skip ROM” command TX 0F11 Issue “write scratchpad" command TX 2611 TAl‘ beginning offset:6 TX 0011 TA2‘ address:@26h TX <2 data="" bytes=""> Write 2 bytes cfdata to scratcl1pad TX Reset Reset pulse RX Presence Presence pulse TX CCh Issue “skip ROM” command TX AAh Issue “read scratchpad" command RX 2611 Read TAl‘ beginning offset:6 RX 0011 Read TA2. address:0026h RX 0711 Read E/S, ending offset:7, flags:0 RX <2 data="" bytes=""> Read scratchpad data and Verify TX Reset Reset pulse RX Presence Presence pulse TX CCh Issue “skip ROM” command TX 5511 Issue “copy scratchpad" command TX 2611 TA] TX 0011 TAZ} TX 0711 E/S TX Reset Reset pulse RX Presence Presence pulse TX CCh Issue “skip ROM” command TX F011 Issue “read memory” command TX 0011 TAl‘ beginning offset:0 TX 0011 TA2‘ addresFflOOh RX <8192 bytes=""> Read entire memory TX Reset Reset pulse RX Presence Presence pulse, done
DS1996
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MEMORY FUNCTION EXAMPLES
Example: Write two data bytes to memory locations 0026h and 0027h (the seventh and 8th bytes of page
1). Read entire memory.
MASTER MODE
DATA (LSB FIRST)
COMMENTS
TX
Reset
Reset pulse (480-960 µs)
RX
Presence
Presence pulse
TX
CCh
Issue skip ROM” command
TX
0Fh
Issue “write scratchpadcommand
TX
26h
TA1, beginning offset=6
TX
00h
TA2, address=0026h
TX
<2 data bytes>
Write 2 bytes of data to scratchpad
TX
Reset
Reset pulse
RX
Presence
Presence pulse
TX
CCh
Issue skip ROM” command
TX
AAh
Issue read scratchpadcommand
RX 26h Read TA1, beginning offset=6
RX
00h
Read TA2, address=0026h
RX
07h
Read E/S, ending offset=7, flags=0
RX
<2 data bytes>
Read scratchpad data and verify
TX
Reset
Reset pulse
RX
Presence
Presence pulse
TX
CCh
Issue skip ROM” command
TX
55h
Issue “copy scratchpadcommand
TX
26h
TA1
TA2 AUTHORIZATION CODE
E/S
TX
00h
TX
07h
TX
Reset
Reset pulse
RX
Presence
Presence pulse
TX
CCh
Issue skip ROM” command
TX
F0h
Issue read memorycommand
TX
00h
TA1, beginning offset=0
TX
00h
TA2, address=0000h
RX
<8192 bytes>
Read entire memory
TX
Reset
Reset pulse
RX
Presence
Presence pulse, done
0 f the cad ing 0 pa sto to more 5 Her. T ansact ctio cs 1
DS1996
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Copy Scratchpad [55H]
This command is used to copy data from the scratchpad to memory. After issuing the copy scratchpad
command, the master must provide a 3-byte authorization pattern which is obtained by reading the
scratchpad for verification. This pattern must exactly match the data contained in the three address
registers (TA1, TA2, E/S, in that order). If the pattern matches, the AA (Authorization Accepted) flag
will be set and the copy will begin. A logic 0 will be transmitted after the data has been copied until a
reset pulse is issued by the master. Any attempt to reset the part will be ignored while the copy is in
progress. Copy typically takes 30 µs.
The data to be copied is determined by the three address registers. The scratchpad data from the
beginning offset through the ending offset, will be copied to memory, starting at the target address.
Anywhere from 1 to 32 bytes may be copied to memory with this command. Whole bytes are copied
even if only partially written. The AA flag will be cleared only by executing a write scratchpad
command.
Read Memory [F0H]
The read memory command may be used to read the entire memory. After issuing the command, the
master must provide the 2-byte target address. After the 2 bytes, the master reads data beginning from the
target address and may continue until the end of memory, at which point logic 1’s will be read. It is
important to realize that the target address registers will contain the address provided. The ending
offset/data status byte is unaffected.
The hardware of the DS1996 provides a means to accomplish error-free writing to the memory section.
To safeguard reading data in the 1-Wire environment and to simultaneously speed up data transfers, it is
recommended to packetize data into data packets of the size of one memory page each. Such a packet
would typically store a 16-bit CRC with each page of data to ensure rapid, error-free data transfers that
eliminate having to read a page multiple times to determine if the received data is correct or not. (See the
Book of DS19xx iButton Standards, Chapter 7 for the recommended file structure to be used with the 1-
Wire environment.)
1-WIRE BUS SYSTEM
The 1-Wire bus is a system which has a single bus master and one or more slaves. In all instances the
DS1996 is a slave device. The bus master is typically a microcontroller. The discussion of this bus
system is broken down into three topics: hardware configuration, transaction sequence, and 1-Wire
signaling (signal types and timing). A 1-Wire protocol defines bus transactions in terms of the bus state
during specified time slots that are initiated on the falling edge of sync pulses from the bus master. For a
more detailed protocol description, refer to Chapter 4 of the Book of DS19xx iButton Standards.
HARDWARE CONFIGURATION
The 1-Wire bus has only a single line by definition; it is important that each device on the bus be able to
drive it at the appropriate time. To facilitate this, each device attached to the 1-Wire bus must have open
drain connection or 3-state outputs. The 1-Wire port of the DS1996 is open drain with an internal circuit
equivalent to that shown in Figure 8. A multidrop bus consists of a 1-Wire bus with multiple slaves
attached. At regular speed the 1-Wire bus has a maximum data rate of 16.3 kbits per second. The speed
can be boosted to 142 kbits per second by activating the Overdrive Mode. The 1-Wire bus requires a
pullup resistor of approximately 5 k.
The idle state for the 1-Wire bus is high. If for any reason a transaction needs to be suspended, the bus
MUST be left in the idle state if the transaction is to resume. If this does not occur and the bus is left low
for more than 16 µs (Overdrive Speed) or more than 120 µs (regular speed), one or more of the devices
on the bus may be reset.
cc BUS MASTER vé DSIBSS l-WIHE PORT 5 m i “X i mm Rx ; _ 5M Tx TX R — RECEIVE Tm |_— 100 OHM : MOSFET
DS1996
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HARDWARE CONFIGURATION Figure 8
TRANSACTION SEQUENCE
The protocol for accessing the DS1996 via the 1-Wire port is as follows:
Initialization
ROM Function Command
Memory Function Command
Transaction/Data
INITIALIZATION
All transactions on the 1-Wire bus begin with an initialization sequence. The initialization sequence
consists of a reset pulse transmitted by the bus master followed by presence pulse(s) transmitted by the
slave(s).
The presence pulse lets the bus master know that the DS1996 is on the bus and is ready to operate. For
more details, see the ”1-Wire Signaling” section.
ROM FUNCTION COMMANDS
Once the bus master has detected a presence, it can issue one of the six ROM function commands. All
ROM function commands are 8 bits long. A list of these commands follows (refer to flowchart in Figure
9).
Read ROM [33H]
This command allows the bus master to read the DS1996’s 8-bit family code, unique 48-bit serial
number, and 8-bit CRC. This command can only be used if there is a single DS1996 on the bus. If more
than one slave is present on the bus, a data collision will occur when all slaves try to transmit at the same
time (open drain will produce a wired-AND result). The resultant family code and 48-bit serial number
will usually result in a mismatch of the CRC.
R
x
= RECEIVE
Tx = TRANSMIT
h ROM [FOH ystcm is initi or their 64-h ion to idcn ition of a c oftha mplctc ices i
DS1996
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Match ROM [55H]
The match ROM command, followed by a 64-bit ROM sequence, allows the bus master to address a
specific DS1996 on a multidrop bus. Only the DS1996 that exactly matches the 64-bit ROM sequence
will respond to the subsequent memory function command. All slaves that do not match the 64-bit ROM
sequence will wait for a reset pulse. This command can be used with a single or multiple devices on the
bus.
Skip ROM [CCH]
This command can save time in a single drop bus system by allowing the bus master to access the
memory functions without providing the 64-bit ROM code. If more than one slave is present on the bus
and a read command is issued following the Skip ROM command, data collision will occur on the bus as
multiple slaves transmit simultaneously (open drain pulldowns will produce a wiredAND result).
Search ROM [F0H]
When a system is initially brought up, the bus master might not know the number of devices on the 1-
Wire bus or their 64-bit ROM codes. The search ROM command allows the bus master to use a process
of elimination to identify the 64-bit ROM codes of all slave devices on the bus. The search ROM process
is the repetition of a simple 3-step routine: read a bit, read the complement of the 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 remaining
number of devices and their ROM codes may be identified by additional passes. See Chapter 5 of the
Book of DS19xx iButton Standards for a comprehensive discussion of a search ROM, including an actual
example.
Overdrive Skip ROM [3CH]
On a single-drop bus this command can save time by allowing the bus master to access the memory
functions without providing the 64-bit ROM code. Unlike the normal Skip ROM command the Overdrive
Skip ROM sets the DS1996 in the Overdrive Mode (OD=1). All communication following this command
has to occur at Overdrive Speed until a reset pulse of minimum 480 µs duration resets all devices on the
bus to regular speed (OD=0).
When issued on a multidrop bus this command will set all Overdrive-capable devices into Overdrive
mode. To subsequently address a specific Overdrive-capable device, a reset pulse at Overdrive speed has
to be issued followed by a Match ROM or Search ROM command sequence. This will shorten the time
for the search process. If more than one slave supporting Overdrive is present on the bus and the
Overdrive Skip ROM command is followed by a read command, data collision will occur on the bus as
multiple slaves transmit simultaneously (open drain pulldowns will produce a wired-AND result).
Overdrive Match ROM [69H]
The Overdrive Match ROM command, followed by a 64-bit ROM sequence transmitted at Overdrive
Speed, allows the bus master to address a specific DS1996 on a multidrop bus and to simultaneously set it
in Overdrive Mode. Only the DS1996 that exactly matches the 64-bit ROM sequence will respond to the
subsequent memory function command. Slaves already in Overdrive mode from a previous Overdrive
Skip or Match command will remain in Overdrive mode. All other slaves that do not match the 64-bit
ROM sequence or do not support Overdrive will return to or remain at regular speed and wait for a reset
pulse of minimum 480 µs duration. The Overdrive Match ROM command can be used with a single or
multiple devices on the bus.
DS1996
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1-WIRE SIGNALING
The DS1996 requires strict protocols to ensure data integrity. The protocol consists of four types of
signaling on one line: Reset Sequence with Reset Pulse and Presence Pulse, Write 0, Write 1 and Read
Data. All these signals except presence pulse are initiated by the bus master. The DS1996 can
communicate at two different speeds, regular speed and Overdrive speed. If not explicitly set into the
overdrive mode, the DS1996 will communicate at regular speed. While in Overdrive Mode the fast timing
applies to all wave forms.
The initialization sequence required to begin any communication with the DS1996 is shown in Figure 10.
A reset pulse followed by a presence pulse indicates the DS1996 is ready to send or receive data given the
correct ROM command and memory function command. The bus master transmits (TX) a reset pulse
(tRSTL, minimum 480 µs at regular speed, 48 µs at Overdrive speed). The bus master then releases the line
and goes into receive mode (RX). The 1-Wire bus is pulled to a high state via the pullup resistor. After
detecting the rising edge on the data contact, the DS1996 waits (tPDH, 15-60 µs at regular speed, 2-6 µs at
Overdrive speed) and then transmits the presence pulse (tPDL, 60-240 µs at regular speed, 8-24 µs at
Overdrive speed).
A Reset Pulse of 480 µs or longer will exit the Overdrive Mode returning the device to regular speed. If
the DS1996 is in Overdrive Mode and the Reset Pulse is no longer than 80 µs the device will remain in
Overdrive Mode.
FUNCTIONS FLOW CHART Figure 9 MASTER 1] ROM MEMORY FUNCTIONS FLOW CHAR (FIGURE 7) ~——.— FROM FIGURE 9 SECOND FART RESET PULSE Dsms T,I 2) PRESENCE PULSE MASTER TX ROM 1. FUNCTION COMMAND 331. N 5577 Fm ocu N READ RoM a MATCH ROM SEARCH ROM SKIP ROM COMMAND COMMAND COMMAND COMMAND TO FIGURE 9 v v v SECOND PART Dsms TX BIT o I) DSIQSggEEAMILV ‘1 MASTER n BITo " Dsme TX BITD I) I BYTE MAerR TX HIV 0 II N N arr n BIT o MAYCH'? *I MATCH? v v D51996 TX BITI I) D51996 Tx I) i SERIAL NUMBER MASTER ‘x arTI 1) 05‘“ Tx BIT I I) 5 “ES MASTER Ix Err I I) N N BIT I 051996 1')( 1) CRC ans ""7”" y Y T ‘ Dsme Tx arr sa 1) MASTERTXB'T“ ' DSIMYXBWSZJ I) MASTER Tx BIT 63 I) BIT ea N Dir en MATCH? MATCH? TO FIGURE 9 v SECOND PART FROM FIGURE 9 SECOND PART To MEMORY FUNCTIONS FLow CHART (FIGURE 7) 1) TO BE TRANSMITTED OR RECEIVED AT OVERDRIVE SP T
DS1996
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ROM FUNCTIONS FLOW CHART Figure 9
1) TO BE TRANSMITTED OR RECEIVED AT OVERDRIVE
SPEED IF OD=1
2) THE PRESENCE PULSE WILL BE SHORT IF OD=1
TO FIGURE 9 FIRST PART son 69?. N avERDRwE DVERDRIVE FROM FIGURE 9 SKIP MATCH FIRST PART MASYER Tx BIT u v MASIEH Tx an I a) BIT I N MATCH? v an as N MATuI‘I FROM FIGURE 9 v FIRsT PARY To FIGURE 9 3) ALWAYS TO BE TRANSMlTTED AT OVERDRIVE SPEED
DS1996
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ROM FUNCTIONS FLOW CHART Figure 9 (cont’d)
3) ALWAYS TO BE TRANSMITTED AT OVERDRIVE SPEED
F MASTER TX “RESET PULSE" MASTER Rx “PRESENCE PULSE" ’{ 1 I ‘— tnsm VPULLLIF VPUL P MIN \ - IH MIN . VIL MAX ( . 0V [RSTL ‘_ gFDL ‘D ‘R <— *="" ‘pdh="" ‘—="" rlsistor="" *="" l="" rea="" the="" mas="" by="" t="" ds="" dc="" 1h="" r="" write-one="" time="" slot="" ‘="" lslor="" :="" [rec="" vpullup="" ,="" vplillup="" min="" \\="" 1‘="" vih="" min="" d81995="" \="" vil="" max="" sampling="" wmnow="" \="" (w="" .m.="" (on:="" 2="" us)="" ‘5="" ”s="" '="" (00:="" ans)="" 4*="" 60="" p5="" 4.="" resistor="">
DS1996
15 of 19
INITIALIZATION PROCEDURE “RESET AND PRESENCE PULSES” Figure 10
Regular Speed Overdrive Speed
480 µs tRSTL < * 48 µs tRSTL < 80 µs
480 µs tRSTH < (includes recovery time) 48 µs tRSTH <
15 µs PDH < 60 µs 2 µs tPDH < 6 µs
60 µs tPDL < 240 µs 7 µs tPDL < 24 µs
* In order not to mask interrupt signaling by other devices on the 1-Wire bus, tRSTL + tR should always be
less than 960 µs.
READ/WRITE TIME SLOTS
The definitions of write and read time slots are illustrated in Figure 11. All time slots are initiated by the
master driving the data line low. The falling edge of the data line synchronizes the DS1996 to the master
by triggering a delay circuit in the DS1996. During write time slots, the delay circuit determines when the
DS1996 will sample the data line. For a read data time slot, if a ”0” is to be transmitted, the delay circuit
determines how long the DS1996 will hold the data line low overriding the 1 generated by the master. If
the data bit is a ”1”, the iButton will leave the read data time slot unchanged.
READ/WRITE TIMING DIAGRAM Figure 11
Write-One Time Slot
Regular Speed Overdrive Speed
60 µs tSLOT < 120 µs 6 µs tSLOT < 16 µs
1 µs tLOW1 < 15 µs 1 µs tLOW1 < 2 µs
1 µs tREC < 1 µs tREC <
RESISTOR
MASTER
DS1996
RESISTOR
MASTER
rite-Zero Time Slot lnsc ‘sun VPULLUP VPuuvuP MIN IH MIN 031993 VIL MAX SAMF'UNG WIN 0V (on; 6 us) 60 us ‘Lowo Read-Data Time Slot <——— (slot=""><— (rec="" +="" vfullup="" i="" i="" vpul="" 9="" min="" \="" 3="" w="" min="" 7="" a.“="" master="" sampling="" \="" vil="" max="" wwoow="" \="" 0v="" ‘="" [‘—="" ‘su="" a="" ‘helease="" ——="" f.="" kown="" ‘—=""><—-—— ‘rdv="" ——=""> RESISTOR
DS1996
16 of 19
READ/WRITE TIMING DIAGRAM Figure 11 (cont’d)
Write-Zero Time Slot
Regular Speed Overdrive Speed
60 µs tLOW0 < tSLOT < 120 µs 6 µs tLOW0 < tSLOT < 16 µs
1 µs tREC < 1 µs tREC <
Read-Data Time Slot
Regular Speed Overdrive Speed
60 µs tSLOT < 120 µs 6 µs tSLOT < 16 µs
1 µs tLOWR < 15 µs 1 µs tLOWR < 2 µs
0 tRELEASE < 45 µs 0 tRELEASE < 4 µs
1 µs tREC < 1 µs tREC <
tRDV = 15 µs tRDV = 2 µs
tSU < 1 µs tSU < 1 µs
RESISTOR
MASTER
DS1996
DC ELECTRICAL CHARACTERISTICS Vpup=2.8V to 6.0V, —40°C to +70°C) PARAMETER SYMBOL RIIN TYP MAX UNITS NOTES Logic 1 VlH 2.2 Vcc +0.3 V 1, 7 Logic 0 VIL -0.3 +0.3 V 1 Output Logic Low @ 4 mA VOL 0.4 V 1 Input Load Current IL 5 uA 2 CAPACITANCE (TA = 25°C) PARAMETER SYMBOL RIIN TYP MAX UNITS NOTES I/O (1-Wirc) Cm am 100 800 pF 5 AC ELECTRICAL CHARACTERISTICS: REGULAR SPEED (-40°C to 70°C) PARAMETER SYMBOL RIIN TYP MAX UNITS NOTES Time Slot tgLOT 60 120 us Write 1 Low Time tum. 1 15 us Write 0 Low Time ILoM 60 120 us Read Data Valid IRDV exactly 15 us Release Time RELEASE 0 15 45 us Read Data Setup tsu 1 us 4 Recovery Time tREc 1 us Reset Time High mm 480 us 3 Reset Time Low IRSTL 480 us 6 Presence Detect High tpDH 15 60 us Presence Detect Low 1pm 60 240 us
DS1996
17 of 19
PHYSICAL SPECIFICATIONS
Size See mechanical drawing
Weight 3.3 grams (F5 package)
Humidity 90% RH at 50°C
Altitude 10,000 feet
Expected Service Life 10 years at 25°C
ABSOLUTE MAXIMUM RATINGS*
Voltage on any Pin Relative to Ground -0.5V to +7.0V
Operating Temperature -40°C to +70°C
Storage Temperature -40°C to +70°C
This is a stress rating only and functional operation of the device at these or any other conditions
above those indicated in the operation sections of this specification is not implied. Exposure to
absolute maximum rating conditions for extended periods of time may affect reliability.
DC ELECTRICAL CHARACTERISTICS (VPUP=2.8V to 6.0V, -40°C to +70°C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
Logic 1
VIH
2.2
VCC +0.3
V
1, 7
Logic 0
VIL
-0.3
+0.3
V
1
Output Logic Low @ 4 mA
VOL
0.4
V
1
Input Load Current
IL
5
µA
2
CAPACITANCE (TA = 25°C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
I/O (1-Wire)
CIN/OUT
100
800
pF
5
AC ELECTRICAL CHARACTERISTICS: REGULAR SPEED (-40°C to 70°C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
Time Slot
tSLOT
60
120
µs
Write 1 Low Time
tLOW1
1
15
µs
Write 0 Low Time
tLOW0
60
120
µs
Read Data Valid
tRDV
exactly 15
µs
Release Time
tRELEASE
0
15
45
µs
Read Data Setup
tSU
1
µs
4
Recovery Time
t
REC
1
µs
Reset Time High
tRSTH
480
µs
3
Reset Time Low
tRSTL
480
µs
6
Presence Detect High
tPDH
15
60
µs
Presence Detect Low
tPDL
60
240
µs
DS1996 AC ELECTRICAL CHARACTERISTICS: OVERDRIVE SPEED (-40°C to 70°C) PARAMETER SYMBOL IVIIN TYP MAX UNITS NOTES Time Slot tgLOT (7 16 115 Write 1 Low Time tum. 1 2 115 Write 0 Low Time tLOM (7 16 [is Read Data Valid IRDV exactly 2 115 Release Time RELEASE 0 1.5 4 [is Read Data Setup tsu 1 [is 4 Recovery Time tREc 1 [15 Reset Time High thTH 48 [is 3 Reset Time Low thTL 48 80 p5 Presence Detect High tpDH 2 6 p5 Presence Detect Low 1pm 7 24 p5
DS1996
18 of 19
AC ELECTRICAL CHARACTERISTICS: OVERDRIVE SPEED (-40°C to 70°C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
Time Slot
tSLOT
6
16
µs
Write 1 Low Time
tLOW1
1
2
µs
Write 0 Low Time
tLOW0
6
16
µs
Read Data Valid
tRDV
exactly 2
µs
Release Time
tRELEASE
0
1.5
4
µs
Read Data Setup
tSU
1
µs
4
Recovery Time
tREC
1
µs
Reset Time High
tRSTH
48
µs
3
Reset Time Low
tRSTL
48
80
µs
Presence Detect High
tPDH
2
6
µs
Presence Detect Low
tPDL
7
24
µs
NOTES:
1. All voltages are referenced to ground.
2. Input load is to ground.
3. An additional reset or communication sequence cannot begin until the reset high time has expired.
4. Read data setup time refers to the time the host must pull the 1-Wire bus low to read a bit. Data is
guaranteed to be valid within 1 µs of this falling edge.
5. Capacitance on the data contact could be 800 pF when power is first applied. If a 5 k resistor is used
to pullup the data line to VCC, 5 ms after power has been applied, the parasite capacitance will not
affect normal communications.
6. The reset low time (tRSTL) should be restricted to a maximum of 960 µs, to allow interrupt signaling,
otherwise, it could mask or conceal interrupt pulses.
7. VIH is a function of the external pullup resistor and the VCC power supply.
REVISION HISTORY REVISION PAGES DATE CHANGED maxim Integrated”
DS1996
REVISION HISTORY
REVISION
DATE
DESCRIPTION
PAGES
CHANGED
070808
Updated the Ordering Information table to only show the lead-free
version (DS1996-F5+). 1
Updated the F5 MicroCan marking to match PCN H020201. 1
Updated the wording in the Parasite Power section. 2
Changed the tPDL(MIN) spec from 8µs to 7µs in Figure 10 and in the AC
Electrical Characteristics: Overdrive Speed table. 15, 18
In the DC Electrical Characteristics table, removed the VOH spec and
changed the VIL(MAX) spec from 0.8V to 0.3V. 17
8/09 Removed the UL#913 bullet in the Common iButton Features section. 1
19
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical
Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
© 2009 Maxim Integrated The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.

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