DS2405Z+ [MAXIM]

Memory Circuit, 64X1, CMOS, PDSO4, 0.137 INCH, ROHS COMPLIANT, SOT-223, 4 PIN;
DS2405Z+
型号: DS2405Z+
厂家: MAXIM INTEGRATED PRODUCTS    MAXIM INTEGRATED PRODUCTS
描述:

Memory Circuit, 64X1, CMOS, PDSO4, 0.137 INCH, ROHS COMPLIANT, SOT-223, 4 PIN

静态存储器 光电二极管 内存集成电路
文件: 总15页 (文件大小:446K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
DS2405  
Addressable Switch  
www.maxim-ic.com  
FEATURES  
PIN ASSIGNMENT  
TSOC PACKAGE  
Open-drain PIO pin is controlled by  
matching 64-bit, laser-engraved registration  
number associated with each device  
Logic level of open drain output can be  
determined over 1-Wire® bus for closed-loop  
control  
TO-92  
GND  
DATA  
PIO  
NC  
NC  
NC  
DS2405  
TOP VIEW  
3.7 X 4.0 X 1.5  
PIO pin sink capability is greater than 4mA  
at 0.4V  
Multiple DS2405s can be identified on a  
common 1-Wire bus and be turned on or off  
independent of other devices on the bus  
Unique, factory-lasered and tested 64-bit  
registration number (8-bit family code +48-  
bit serial number +8-bit CRC tester) assures  
absolute identity because no two parts are  
alike  
1
2 3  
Built-in multidrop controller ensures  
compatibility with other MicroLAN products  
Reduces control, address, data, and power to  
a single data pin  
Directly connects to a single port pin of a  
microprocessor and communicates at up to  
16.3kbits/s  
8-bit family code specifies DS2405  
communications requirements to reader  
8-bit cyclic redundancy check ensures error-  
free selection  
Zero standby power required  
Low cost TO-92, SOT-223, or 6-pin TSOC  
surface mount package  
1 2 3  
TOP VIEW  
BOTTOM VIEW  
See Mech.  
Drawings Section  
NOTE: The leads of TO-92 packages on tape-and-reel are  
formed to approximately 100 mils (2.54 mm) spacing. For  
details refer to drawing 56-G0006-003.  
PIN DESCRIPTION TSOC  
Pin 1 - Ground  
Pin 2 - Data  
Pin 3 - PIO  
Pin 1 - Ground  
Pin 2 - Data  
Pin 3 - PIO  
1-Wire communication operates over a wide  
voltage range of 2.8V to 6.0V from -40°C to  
+85°C  
Pin 4 - Ground  
Pin 4-6 -No Connect  
1-Wire is a registered trademark of Dallas Semiconductor.  
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071107  
DS2405  
ORDERING INFORMATION  
DS2405  
TO-92 package  
DS2405Z  
4-pin SOT-223 package  
DS2405P  
6-pin TSOC package  
DS2405/T&R  
DS2405Z/T&R  
DS2405P/T&R  
Tape & Reel version of DS2405  
Tape & Reel version of DS2405Z  
Tape & Reel version of DS2405P  
DESCRIPTION  
The DS2405 Addressable Switch is an open drain N-channel transistor that can be turned on or off by  
matching the 64-bit factory-lasered registration number within each part. The 64-bit number consists of  
an 8-bit family code, a unique 48-bit serial number, and an 8-bit cyclic redundancy check.  
Communication with the DS2405 follows the standard Dallas Semiconductor 1-Wire protocol and can be  
accomplished with a single port pin of a microcontroller. Multiple DS2405 devices can reside on a  
common 1-Wire bus creating a MicroLAN. The network controller circuitry is embedded within the chip  
including a search algorithm to determine the identity of each DS2405 on the network. The open drain  
output (PIO pin) for each DS2405 on the MicroLan can be independently toggled on or off whether there  
is one or many devices sharing the same 1-Wire bus. The logic level of the PIO pin for each device on the  
MicroLan can also be individually sensed and reported to the bus master.  
OVERVIEW  
The DS2405 Addressable Switch provides a means for assigning an electronically readable identification  
to a particular node or location with additional control capability provided by an open drain N-channel  
MOSFET that can be remotely switched and sensed via communication over the 1-Wire bus. The DS2405  
contains a factory-lasered registration number that includes a unique 48-bit serial number, an 8-bit CRC,  
and an 8-bit family code (05h). The 64-bit ROM portion of the DS2405 not only creates an absolutely  
unique electronic identification for the device itself but also is a means to locate and change or obtain the  
state of the switch that is associated with the 64-bit ROM. The structure of the 64-bit ROM is shown in  
Figure 1. The device derives its power entirely from the 1-Wire bus by storing energy on an internal  
capacitor during periods of time when the signal line is high and continues to operate off of this “parasite”  
power source during the low times of the 1-Wire line until it returns high to replenish the parasite  
(capacitor) supply. The DS2405 uses the standard Dallas Semiconductor 1-Wire protocol for data  
transfers, with all data being read and written least significant bit first. Communication to and from the  
DS2405 requires a single bidirectional line that is typically the port pin of the microcontroller. The 1-  
Wire bus master (microcontroller) must first issue one of five ROM function commands: 1) Read ROM,  
2) Match ROM, 3) Search ROM, 4) Skip ROM, and 5) Active-Only Search ROM. These commands  
operate on the 64-bit lasered ROM portion of each device and can singulate a specific device if many are  
present on the 1-Wire line as well as indicate to the bus how many and what type of each device is  
present. The protocol required for these ROM function commands is described in Figure 4. After a ROM  
function command is successfully executed, the open drain output can be toggled or its current status  
determined via the 1-Wire bus.  
1-WIRE BUS SYSTEM  
The 1-Wire bus is a system that has a single bus master and one or more slaves. In all instances, the  
DS2405 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 type and timing). For a more detailed protocol description, refer to Chapter 4 of the Book of  
DS19xx iButton® Standards.  
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DS2405  
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 an  
open drain connection or 3-state outputs. The DS2405 is an open drain part with an internal circuit  
equivalent to that shown in Figure 2. The bus master can be the same equivalent circuit. If a bidirectional  
pin is not available, separate output and input pins can be tied together. The bus master requires a pullup  
resistor at the master end of the bus, with the bus master circuit equivalent to the one shown in Figure 3.  
The value of the pullup resistor should be approximately 5 kΩ for short line lengths. A multidrop bus  
consists of a 1-Wire bus with multiple slaves attached. The 1-Wire bus has a maximum data rate of  
16.3kbits/s.  
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 120 μs, one or more of the devices on the bus may be reset. In addition, the state of the PIO  
pin for one or more of the DS2405s on the bus may return to its default (off) condition.  
DS2405 MEMORY MAP Figure 1  
8-Bit CRC Code  
48-Bit Serial Number  
8-Bit Family Code (05h)  
MSB  
LSB MSB  
LSB MSB  
LSB  
DS2405 EQUIVALENT CIRCUIT Figure 2  
3 of 15  
DS2405  
BUS MASTER CIRCUIT Figure 3  
A) Open Drain  
To data connection  
of DS2405  
B) Standard TTL  
To data connection  
of DS2405  
TRANSACTION SEQUENCE  
The sequence for accessing the DS2405 via the 1-Wire port is as follows:  
Initialization  
ROM Function Command  
Read 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 a Presence Pulse(s) transmitted by the  
slave(s).  
The Presence Pulse lets the bus master know that at least one DS2405 is on the bus and is ready to  
operate. For more details, see the “1-Wire Signaling” section.  
4 of 15  
DS2405  
ROM FUNCTION COMMANDS  
Once the bus master has detected a presence, it can issue one of five ROM function commands. All ROM  
function commands are 8 bits long. A list of these commands follows (refer to flowchart in Figure 4).  
Read ROM [33h]  
This command allows the bus master to read the DS2405’s 8-bit family code, unique 48-bit serial  
number, and 8-bit CRC. This command can be used only if there is a single DS2405 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).  
Match ROM [55h]  
The Match ROM command, followed by a 64-bit ROM sequence, allows the bus master to address a  
specific device on a multidrop bus. All devices that do not match the 64-bit ROM sequence will wait for a  
Reset Pulse. The DS2405 that exactly matches the 64-bit ROM sequence will toggle the state of its PIO  
pin after the 64th bit of the match is entered. If the open drain N-channel device was off, it will be turned  
on and vice versa. After the last bit of the ROM sequence is received from the bus master and the PIO pin  
of the selected DS2405 has toggled, additional read time slots issued by the bus master will cause the  
DS2405 to output the logic state of its PIO pin onto the 1-Wire bus. If the pulldown is on and the PIO pin  
is a logical 0, the DS2405 will respond with read-0 time slots. If the pulldown is off and the PIO pin is a  
logical 1 (external pullup is required), the DS2405 will respond with read-1 time slot. Each additional  
read time slot issued by the bus master will continue to indicate the state of the PIO pin until a Reset  
Pulse is received from the bus master.  
Search ROM [F0h]  
When a system is initially interrogated, the bus master may 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. This process of  
elimination involves repeated application of a simple three-step procedure where the bus master starts by  
reading a bit position in the 64-bit ROM, followed by reading the complement of that bit position, and  
finally writing to all the devices still involved in the search the desired logic value for that bit position. An  
example is shown below and a flowchart for the search algorithm can be found in the “Book of DS19xx  
iButton Standards.”  
Four devices are connected to the 1-Wire bus. Their binary ROM contents are listed below:  
device 1: xxxxxx10101100  
device 2: xxxxxx01010101  
device 3: xxxxxx10101111  
device 4: xxxxxx10001000  
The x’s represent the higher remaining bits. Shown are the lowest 8 bits of the ROM contents. The least  
significant bit is to the right in this representation. The search process runs as follows:  
1. The master begins the initialization sequence by issuing a Reset Pulse. The devices respond by issuing  
Presence Pulses.  
2. The master will then issue the Search ROM command on the 1-Wire bus.  
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DS2405  
3. The master reads 1 bit from the 1-Wire bus. Each device will respond by placing the value of the first  
bit of its respective ROM data onto the 1-Wire bus. Devices 1 and 4 will place a 0 onto the 1-Wire  
bus; that is, they pull it low. Devices 2 and 3 will send a 1 by allowing the line to stay high. The result  
is the logical AND of all devices on the line; therefore the master reads a 0. The master will issue  
another read time slot. Since the ROM Search command is being executed, all devices respond to this  
second read by placing the complement of the first bit of their respective ROM data onto the 1-Wire  
Bus. Devices 1 and 4 will send a 1; devices 2 and 3 will send a 0. Thus the 1-Wire bus will be pulled  
low. The master again reads a 0 for the complement of the first ROM data bit. This tells the master  
that there are devices on the bus that have a 0 in the first position and others that have a 1. If all  
devices had a 0 in this bit position, the reading would be 01; if the bit position contained a 1, the result  
would be 10. (Note that the 11 condition indicates that no devices are present on the 1-Wire bus.)  
4. The master now decides to write a 0 on the 1-Wire bus. This deselects Devices 2 and 3 for the  
remainder of the search pass, leaving only devices 1 and 4 participating in the search process.  
5. The master performs two more reads and receives a 0 followed by a 1 bit. This indicates that all active  
devices have a 0 in this bit position of their ROM.  
6. The master then writes a 0 to keep devices 1 and 4 selected.  
7. The master executes two reads and receives two 0 bits. This again indicates that both 1 and 0 exist as  
the third bit of the ROM of the active devices.  
8. The master again writes a 0. This deselects device 1, leaving device 4 as the only active device.  
9. Subsequent reads to the end of the ROM will not show bit conflicts. Therefore, they directly tell the  
master the ROM contents of the active device. After having learned any new ROM bit, the master has  
to resend this bit to keep the device selected. As soon as all ROM bits of the device are known and the  
last bit is resent by the master, the device is ready to output the state of the PIO pin using additional  
read time slots.  
10. The master must learn the other devices’ ROM data. Therefore, it starts another ROM Search  
sequence by repeating steps 1 through 7.  
11. At the highest bit position, where the master wrote a 0 at the first pass (step 8), it now writes a 1. This  
deselects device 4, leaving device 1 active.  
12. As in step 9, subsequent reads to the end of the ROM will not show bit conflicts. This completes the  
second ROM Search pass where the master has learned another ROM’s contents.  
13. The master must learn the other devices’ ROM data. Therefore, it starts another ROM Search  
sequence by repeating steps 1 to 3.  
14. At the second highest bit position where the master wrote a 0 at the first pass (step 4), it now writes a  
1. This deselects devices 1 and 4, leaving devices 2 and 3 active.  
15. The master sends two read time slots and receives two 0 bits, indicating a bit conflict.  
16. The master again decides to write a 0. This deselects device 3, leaving device 2 as the only active  
device.  
17. As in step 9, subsequent reads to the end of the ROM will not show bit conflicts. This completes the  
third ROM Search pass where the master has learned another ROM’s contents.  
6 of 15  
DS2405  
18. The master must learn the other devices’ ROM data. Therefore it starts another ROM Search sequence  
by repeating steps 13 to 15.  
19. At the highest bit position where the master wrote a 0 at the previous pass (step 16), it now writes a 1.  
This deselects device 2, leaving device 3 active.  
20. As in step 17, subsequent reads to the end of the ROM will not show bit conflicts. This completes the  
fourth ROM Search pass where the master has learned another ROM’s contents.  
After one complete pass, the bus master knows the contents of the 64-bit ROM in one device. Subsequent  
passes will reveal the total number of devices and their individual ROM codes. In addition, after each  
complete pass of the search that successfully determines the 64-bit ROM for a specific device on the  
multidrop bus, that particular device can be individually accessed as if a Match ROM has been issued  
since all other devices will have dropped out of the search process and are waiting for a Reset Pulse. The  
DS2405 that was discovered by the search process will not toggle the state of its PIO pin at the end of the  
search, but additional read time slots issued by the bus master after the search is completed will cause the  
DS2405 to output the logic state of its PIO pin onto the 1-Wire bus. If the pulldown is on and the PIO pin  
is a logical 0, the DS2405 will respond with read-0 time slots. If the pulldown is off and the PIO pin is a  
logical 1 (external pullup is required), the DS2405 will respond with read-1 time slots. Each additional  
read time slot issued by the bus master will continue to indicate the state of the PIO pin until a Reset  
Pulse is received from the bus master. The combination of Match ROM and Search ROM allows the user  
to change the state of the PIO pin and report the current state (Match ROM) or simply report the current  
state of the PIO pin without changing it (Search ROM).  
Active-Only Search ROM [ECh]  
The Active-Only Search ROM command operates similarly to the Search ROM command except that  
only devices with their output pulldown turned on are allowed to participate in the search. This provides  
an efficient means for the bus master to determine devices on a multidrop system that are active (PIO pin  
driven low). After each pass of the active-only search that successfully determines the 64-bit ROM for a  
specific device on the multidrop bus with its output pulldown turned on, that particular device can be  
individually accessed as if a Match ROM had been issued since all other devices will have dropped out of  
the active-only search process and are waiting for a Reset Pulse. The DS2405 that was discovered by the  
active-only search process will not toggle the state of its PIO pin at the end of the search, but additional  
read time slots issued by the bus master after the search is completed will cause the DS2405 to output the  
logic state of the PIO pin (see Figure 2) onto the 1-wire bus. Since the Active-Only Search ROM  
command only operates on devices with their pulldown on, the internal CONTROL signal for each of  
these parts is always a logical 1. With CONTROL=1, the selected DS2405 will respond to the bus master  
with read-0 time slots after an active-only search pass is successfully completed. Each additional read  
time slot issued by the bus master will continue to appear as a read-0 until a Reset Pulse is received from  
the bus master. If the CONTROL signal is a logical 0 for any DS2405, that device will not participate in  
the Active-Only Search. The combination of Search ROM and Active-Only Search ROM allows the user  
to search in the most efficient manner depending on the requirements. If the bus master interrogates a  
multidrop system comprised of DS2405s whose PIO conditions are unknown, the Active-Only Search  
can quickly determine which devices are turned on. The two commands also allow the bus master to  
separately determine the state of the PIO pin and the internal CONTROL signal which may be useful in  
detecting certain conditions. If Search ROM returns read-0 time slots (PIO=logical 0) for a given device,  
it may be due to that particular DS2405 driving its PIO pin low, or under certain conditions the logical 0  
may be caused by some other device holding PIO low. If that same device is found using an active-only  
search, CONTROL must be a logical 1 and the PIO pin is being held low by the DS2405. If that same  
7 of 15  
DS2405  
device is not found using an active-only search, CONTROL must be a logical 0 and the PIO pin is being  
held low by some other device or perhaps a fault condition such as a PIO shorted to ground. A second  
fault condition may be detected if Search ROM for a given device returns read-1 time slots (PIO=logical  
1) but Active-Only Search ROM is successful (CONTROL=logical 1) and returns read-0 time slots for  
the same device, indicating the possibility that PIO may be shorted to a positive voltage.  
8 of 15  
DS2405  
ROM FUNCTIONS FLOW CHART Figure 4  
9 of 15  
DS2405  
ROM FUNCTIONS FLOW CHART Figure 4 (cont.)  
10 of 15  
DS2405  
Skip ROM [CCh]  
The complete 1-Wire protocol for all Dallas Semiconductor iButtons contains a Skip ROM command.  
Since the DS2405 contains only the 64-bit ROM with no additional data fields, the Skip ROM is not  
applicable and will cause no further activity on the 1-Wire bus if executed. The DS2405 does not interfere  
with other 1-Wire parts on a multidrop bus that do respond to a Skip ROM (for example, a DS2405 and  
DS1994 on the same bus).  
1-WIRE SIGNALING  
The DS2405 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 initialization sequence required to begin any communication with the DS2405 is shown in Figure 5.  
A Reset Pulse followed by a Presence Pulse indicates the DS2405 is ready to send or receive data given  
the correct ROM command.  
The bus master transmits (TX) a Reset Pulse (tRSTL, minimum 480μs). 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 5kΩ pullup resistor.  
After detecting the rising edge on the data pin, the DS2405 waits (tPDH, 15-60μs) and then transmits the  
Presence Pulse (tPDL, 60-240μs).  
INITIALIZATION PROCEDURE “RESET AND PRESENCE PULSES” Figure 5  
RESISTOR  
480μs tRSTL < *  
480μs tRSTH < (includes recovery time)  
MASTER  
15μs tPDH < 60μs  
DS2405  
60μs tPDL < 240μs  
In order not to mask interrupt signaling by other devices on the 1-Wire bus, tRSTL + tR should always  
be less than 960μs.  
11 of 15  
DS2405  
READ/WRITE TIME SLOTS  
The definitions of write and read time slots are illustrated in Figure 6. All time slots are initiated by the  
master driving the data line low. The falling edge of the data line synchronizes the DS2405 to the master  
by triggering a delay circuit in the DS2405. During write time slots, the delay circuit determines when the  
DS2405 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 DS2405 will hold the data line low overriding the “1” generated by the master.  
If the data bit is a 1, the device will leave the read data time slot unchanged.  
READ/WRITE TIMING DIAGRAM Figure 6  
Write-1 Time Slot  
RESISTOR  
60μs tSLOT < 120μs  
1μs tLOW1 < 15μs  
MASTER  
1μs tREC < ∞  
Write-0 Time Slot  
60μs tLOW0 < tSLOT < 120μs  
1μs tREC < ∞  
12 of 15  
DS2405  
READ/WRITE TIMING DIAGRAM Figure 6 (cont.)  
Read-Data Time Slot  
60μs tSLOT < 120μs  
RESISTOR  
1μs tLOWR < 15μs  
0 tRELEASE < 45μs  
1μs tREC < ∞  
tRDV = 15μs  
MASTER  
DS2405  
tSU < 1μs  
CRC GENERATION  
To validate the data transmitted from the DS2405, the bus master may generate a CRC value from the  
data as it is received. This generated value is compared to the value stored in the last 8 bits of the  
DS2405. If the two CRC values match, the transmission is error-free.  
The equivalent polynomial function of this CRC is:  
CRC = x8 + x5 + x4 + 1  
For more details, see the Book of DS19xx iButton Standards.  
13 of 15  
DS2405  
ABSOLUTE MAXIMUM RATINGS*  
Voltage on any Pin Relative to Ground  
Operating Temperature Range  
Storage Temperature Range  
-0.5V to +7.0V  
-40°C to +85°C  
-55°C to +125°C  
Solder Temperature  
See J-STD-020A Specification  
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  
(-40°C to +85°C; VPUP = 2.8V to 6.0V)  
PARAMETER  
SYMBOL MIN  
TYP  
MAX  
VCC +0.3  
+0.8  
UNITS NOTES  
Logic 1  
Logic 0  
VIH  
VIL  
VOL  
VOH  
IL  
2.2  
V
V
V
1,6,8  
1,10  
1
-0.3  
Output Logic Low @ 4 mA  
Output Logic High  
Input Load Current (DATA pin)  
Input Resistance (PIO pin)  
0.4  
VPUP  
5
6.0  
V
μA  
MΩ  
1,2  
3
9
IR  
10  
CAPACITANCE  
PARAMETER  
Capacitance DATA pin  
Capacitance PIO pin  
(tA = 25°C)  
SYMBOL MIN  
TYP  
MAX  
800  
10  
UNITS NOTES  
CD  
CP  
pF  
pF  
7
AC ELECTRICAL CHARACTERISTICS  
(-40°C to +85°C; VPUP =2.8V to 6.0V)  
PARAMETER  
Time Slot  
SYMBOL MIN  
TYP  
MAX  
120  
15  
UNITS NOTES  
tSLOT  
tLOW1  
tLOW0  
tLOWR  
tRDV  
tRELEASE  
tSU  
tREC  
60  
1
60  
1
μs  
Write-1 Low Time  
Write-0 Low Time  
Read Low Time  
Read Data Valid  
Release Time  
Read Data Setup  
Recovery Time  
Reset Time High  
Reset Time Low  
Presence Detect High  
Presence Detect Low  
12  
μs  
μs  
μs  
μs  
μs  
μs  
μs  
μs  
μs  
μs  
μs  
120  
15  
12  
11  
15  
15  
0
45  
1
5
1
tRSTH  
tRSTL  
tPDH  
480  
480  
15  
4
13  
960  
60  
240  
tPDL  
60  
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DS2405  
NOTES:  
1. All voltages are referenced to ground.  
2. VPUP = external pullup voltage.  
3. Input load is to ground.  
4. An additional reset or communication sequence cannot begin until the reset high time has expired.  
5. 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 1μs of this falling edge and will remain valid for 14μs minimum (15μs  
total from falling edge on 1-Wire bus).  
6. VIH is a function of the external pull-up resistor and the VCC supply.  
7. Capacitance on the data pin could be 800pF when power is first applied. If a 5kΩ resistor is used to  
pull-up the data line to VCC, 5μs after power has been applied the parasite capacitance will not affect  
normal communications.  
8. VIH for PIO pin should always be greater than or equal to VPUP -0.3V.  
9. Input resistance is to ground.  
10. Under certain low voltage conditions VILMAX may have to be reduced to as much as 0.5V to always  
guarantee a Presence Pulse.  
11. The optimal sampling point for the master is as close as possible to the end of the 15μs tRDV period  
without exceeding tRDV. For the case of a Read 1 time slot, this maximizes the amount of time for the  
pull-up resistor to recover the line to a high level. For a Read 0 time slot, it ensures that a read will  
occur before the fastest 1-Wire device(s) release the line.  
12. The duration of the low pulse sent by the master should be a minimum of 1μs with a maximum value  
as short as possible to allow time for the pull-up resistor to recover the line to a high level before the  
1-Wire device samples in the case of a Write 1 Low Time, or before the master samples in the case of  
a Read Low Time.  
13. The Reset Low Time (tRSTL) should be restricted to a maximum of 960μs to allow interrupt signaling;  
otherwise, it could mask or conceal interrupt pulses.  
15 of 15  

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Addressable Switch
DALLAS

DS2406

Dual Addressable Switch Plus 1K-Bit Memory
DALLAS

DS2406

Dual Addressable Switch Plus 1Kb Memory
MAXIM

DS2406+

Dual Addressable Switch Plus 1kbit Memory
DALLAS

DS2406+

Dual Addressable Switch Plus 1Kb Memory
MAXIM

DS2406+R

Dual Addressable Switch Plus 1kbit Memory
DALLAS

DS2406+T

Dual Addressable Switch Plus 1kbit Memory
DALLAS

DS2406+T&R

OTP ROM, 1KX1, CMOS, PBCY3, LEAD FREE, TO-92, 3 PIN
MAXIM