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| 型号： | DS2704G+T&R |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/18页 |
| 文件大小： | 0K |
| 描述： | IC EEPROM 1.25KBIT 6TDFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 10,000 |
| 格式 - 存储器： | EEPROMs - 串行 |
| 存储器类型： | EEPROM |
| 存储容量： | 1.25K（32B x 5 页） |
| 接口： | 1 线 串行 |
| 电源电压： | 2.5 V ~ 5.5 V |
| 工作温度： | -30°C ~ 85°C |
| 封装/外壳： | 6-WDFN 裸露焊盘 |
| 供应商设备封装： | 6-TDFN 裸露焊盘（3x3） |
| 包装： | 带卷 (TR) |
DS2704: 1280-Bit EEPROM with SHA-1 Authentication
CRC GENERATION
The DS2704 has an 8-bit CRC stored in the most significant byte of its 1-Wire net address and generates a CRC
during some command protocols. To ensure error-free transmission of the address, the host system can compute a
CRC value from the first 56 bits of the address and compare it to the CRC from the DS2704.
The host system is responsible for verifying the CRC value and taking action as a result. The DS2704 does not
compare CRC values and does not prevent a command sequence from proceeding as a result of a CRC mismatch.
Proper use of the CRC can result in a communication channel with a very high level of integrity.
The CRC can be generated by the host using a circuit consisting of a shift register and XOR gates as shown in
Figure 3, or it can be generated in software using the polynomial X 8 + X 5 + X 4 + 1. Additional information about the
Dallas 1-Wire CRC is available in Application Note 27: Understanding and Using Cyclic Redundancy Checks with
Dallas Semiconductor iButton ? Products ( www.maxim-ic.com/appnoteindex ).
In the circuit in Figure 3, 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 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.
Figure 3. 1-Wire CRC Generation Block Diagram
INPUT
MSb
XOR
XOR
LSb
XOR
During some command sequences, the DS2704 also generates an 8-bit CRC and provides this value to the bus
master to facilitate validation for the transfer of command, address, and data from the bus master to the DS2704.
The DS2704 computes an 8-bit CRC for the command and address bytes received from the bus master for the
Read Memory, Read Status and Read/Generate CRC commands to confirm that these bytes have been received
correctly. The CRC generator on the DS2704 is also used to provide verification of error-free data transfer as each
EEPROM page is sent to the master during a Read Data/Generate CRC command and for the 8 bytes of
information in the Status memory field.
In each case where a CRC is used for data transfer validation, the bus master must calculate the CRC value using
the same polynomial function and compare the calculated value to the CRC either stored in the DS2704 Net
Address or computed by the DS2704. The comparison of CRC values and decision to continue with an operation
are determined entirely by the bus master. There is no circuitry in the DS2704 that prevents the a command
sequence from proceeding if the stored or calculated CRC from the DS2704 and the calculated CRC from the host
do not match.
HARDWARE CONFIGURATION
Because the 1-Wire bus has only a single line, 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 connect to the bus with open-drain
or tri-state output drivers. The DS2704 uses an open-drain output driver as part of the bidirectional interface
circuitry shown in Figure 4. If a bidirectional pin is not available on the bus master, separate output and input pins
can be connected together.
The 1-Wire bus must have a pullup resistor at the bus-master end of the bus. A value of between 2k Ω and 5k Ω is
recommended. The idle state for the 1-Wire bus is high. If, for any reason, a bus transaction must be suspended,
the bus must be left in the idle state to properly resume the transaction later. Note that if the bus is left low for more
than t RSTL , slave devices on the bus begin to interpret the low period as a reset pulse, effectively terminating the
transaction.
iButton is a registered trademark of Dallas Semiconductor.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DS2704K | 功能描述:电可擦除可编程只读存储器 RoHS:否 制造商:Atmel 存储容量:2 Kbit 组织:256 B x 8 数据保留:100 yr 最大时钟频率:1000 KHz 最大工作电流:6 uA 工作电源电压:1.7 V to 5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 |
| DS2704REVKIT+ | 制造商:Maxim Integrated Products 功能描述:RMS POWER DETECTOR - Boxed Product (Development Kits) |
| DS2704RG+ | 功能描述:电可擦除可编程只读存储器 RoHS:否 制造商:Atmel 存储容量:2 Kbit 组织:256 B x 8 数据保留:100 yr 最大时钟频率:1000 KHz 最大工作电流:6 uA 工作电源电压:1.7 V to 5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 |
| DS2704RG+T&R | 功能描述:电可擦除可编程只读存储器 RoHS:否 制造商:Atmel 存储容量:2 Kbit 组织:256 B x 8 数据保留:100 yr 最大时钟频率:1000 KHz 最大工作电流:6 uA 工作电源电压:1.7 V to 5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 |
| DS2704R-K | 功能描述:电可擦除可编程只读存储器 RoHS:否 制造商:Atmel 存储容量:2 Kbit 组织:256 B x 8 数据保留:100 yr 最大时钟频率:1000 KHz 最大工作电流:6 uA 工作电源电压:1.7 V to 5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 |
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