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参数资料
| 型号： | DS2422X |
| 厂商： | DALLAS SEMICONDUCTOR |
| 元件分类： | Memory IC:Other |
| 英文描述： | SPECIALTY MEMORY CIRCUIT, UUC |
| 文件页数： | 19/23页 |
| 文件大小： | 146K |
| 代理商： | DS2422X |
DS2422/DS2423
021998 5/23
WRITING WITH VERIFICATION
To write data to the DS242X, 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.
Under certain conditions (see Write
Scratchpad command) the 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 master can compare it to
the value it has calculated itself to decide if the commu-
nication was successful and proceed to the Copy
Scratchpad command. If the master could not receive
the CRC16, it has to send the Read Scratchpad com-
mand to read back the scratchpad to verify data integ-
rity. As preamble to the scratchpad data, the DS242X
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. 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 indi-
cates 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 master
can continue reading and verifying every data byte.
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 regis-
ters TA1, TA2 and E/S. The master may obtain the con-
tents 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 DS242X has received
these bytes correctly, 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 DS242X takes place either at regu-
lar speed (default, OD = 0) or at Overdrive Speed
(OD = 1). If not explicitly set into the Overdrive Mode the
DS242X assumes regular speed.
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 off-
set at which the 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 executing the Write Scratchpad command the
CRC generator inside the DS242X (see Figure 12) cal-
culates a CRC over the entire data stream, starting at
the command code and ending at the last data byte sent
by the 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 master and all the data bytes.
The master may end the Write Scratchpad command at
any time. However, if the ending offset is 11111b, the
master may send 16 read time slots and will receive the
CRC generated by the DS242X.
The memory address range of the DS2422 is 0000H to
007FH and 0000H to 01FFH for the DS2423, respec-
tively. If the bus master sends a target address higher
than this, the internal circuitry of the chip will set the nine
(DS2422) or seven (DS2423) most significant address
bits to zero as they are shifted into the internal address
register. The Read Scratchpad command will reveal the
target address as it will be used by the DS242X. The
master will identify such address modifications by
comparing the target address read back to the target
address transmitted. If the master does not read the
scratchpad, a subsequent copy scratchpad command
will not work since the most significant bits of the target
address the master sends will not match the value the
DS242X expects.
Read Scratchpad Command [AAH]
This command is used to verify scratchpad data and tar-
get address. After issuing the read scratchpad com-
mand, the master begins reading. The first two bytes
will be the target address. The next byte will be the end-
ing offset/data status byte (E/S) followed by the scratch-
pad data beginning at the byte offset (T4: T0). The mas-
ter may read data until the end of the scratchpad after
which the data read will be all logic 1s.
Copy Scratchpad [5AH]
This command is used to copy data from the scratchpad
to memory. After issuing the copy scratchpad com-
mand, the master must provide a 3–byte authorization
pattern which can be obtained by reading the scratch-
pad for verification. This pattern must exactly match the
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相关代理商/技术参数 |
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| DS2423 | 制造商:DALLAS 制造商全称:Dallas Semiconductor 功能描述:4kbit 1-Wire RAM with Counter |
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| DS2423D/T&R | 功能描述:IC SRAM 4KBIT 6FCHIP RoHS:否 类别:集成电路 (IC) >> 存储器 系列:- 标准包装:150 系列:- 格式 - 存储器:EEPROMs - 串行 存储器类型:EEPROM 存储容量:4K (2 x 256 x 8) 速度:400kHz 接口:I²C，2 线串口 电源电压:2.5 V ~ 5.5 V 工作温度:-40°C ~ 85°C 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-DFN（2x3） 包装:管件 产品目录页面:1445 (CN2011-ZH PDF) |
| DS2423MRAB0 | 制造商:Thomas & Betts 功能描述:300A,NLT,3P4W,MG,423,3P480V |
| DS2423P | 功能描述:静态随机存取存储器 RoHS:否 制造商:Cypress Semiconductor 存储容量:16 Mbit 组织:1 M x 16 访问时间:55 ns 电源电压-最大:3.6 V 电源电压-最小:2.2 V 最大工作电流:22 uA 最大工作温度:+ 85 C 最小工作温度:- 40 C 安装风格:SMD/SMT 封装 / 箱体:TSOP-48 封装:Tray |
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