參數(shù)資料
型號(hào)： DS1985
英文描述： 16-kbit Add-Only iButton
中文描述： 16K位只添加iButton®
文件頁(yè)數(shù)： 5/25頁(yè)
文件大?。?/td> 440K
代理商： DS1985
DS1985
5 of 25
16384 BITS EPROM
The memory map in Figure 4 shows the 16384 bits EPROM section of the DS1985 which is configured
as 64 pages of 32 bytes each. The 8-bit scratchpad is an additional register that acts as a buffer when
programming the memory. Data is first written to the scratchpad and then verified by reading a 16-bit
CRC from the DS1985 that confirms proper receipt of the data and address. If the buffer contents are
correct, a programming voltage should be applied and the byte of data will be written into the selected
address in memory. This process ensures data integrity when programming the memory. The details for
reading and programming the 16384 bits EPROM portion of the DS1985 are given in the Memory
Function Commands section.
EPROM STATUS BYTES
In addition to the 16384 bits of data memory the DS1985 provides 704 bits of Status Memory accessible
with separate commands.
The EPROM Status Bytes can be read or programmed to indicate various conditions to the software
interrogating the DS1985. The first 8 bytes of the EPROM Status Memory (addresses 000 to 007H)
contain the Write Protect Page bits which inhibit programming of the corresponding page in the 16384-bit
main memory area if the appropriate write protection bit is programmed. Once a bit has been
programmed in the Write Protect Page section of the Status Memory, the entire 32-byte page that
corresponds to that bit can no longer be altered but may still be read.
The next 8 bytes of the EPROM Status Memory (addresses 020 to 027H) contain the Write Protect bits
which inhibit altering the Page Address Redirection Byte corresponding to each page in the 16384-bit
main memory area.
The following 8 bytes within the EPROM Status Memory (addresses 040 to 047H) are reserved for use
by the iButton operating software TMEX. Their purpose is to indicate which memory pages are already in
use. Originally, all of these bits are unprogrammed, indicating that the device does not store any data. As
soon as data is written to any page of the device under control of TMEX, the bit inside this bitmap
corresponding to that page will be programmed to 0, marking this page as used. These bits are application
flags only and have no impact on the internal logic of the DS1985.
The next 64 bytes of the EPROM Status Memory (addresses 100H to 13FH) contain the Page Address
Redirection Bytes which indicate if one or more of the pages of data in the 16384 bits EPROM section
have been invalidated by software and redirected to the page address contained in the appropriate
redirection byte. The hardware of the DS1985 makes no decisions based on the contents of the Page
Address Redirection Bytes. These additional bytes of Status EPROM allow for the redirection of an entire
page to another page address, indicating that the data in the original page is no longer considered relevant
or valid. With EPROM technology, bits within a page can be changed from a logical 1 to a logical 0 by
programming, but cannot be changed back. Therefore, it is not possible to simply rewrite a page if the
data requires changing or updating, but with space permitting, an entire page of data can be redirected to
another page within the DS1985 by writing the one’s complement of the new page address into the Page
Address Redirection Byte that corresponds to the original (replaced) page.
This architecture allows the user’s software to make a “data patch” to the EPROM by indicating that a
particular page or pages should be replaced with those indicated in the Page Address Redirection Bytes.
To leave an authentic audit trail of data patches, it is recommended to also program the write protect bit
of the Page Address Redirection Byte, after the page redirection is programmed. Without this protection,
it is still possible to modify the Page Address Redirection Byte, making it point to a different memory
page than the true one.
相關(guān)PDF資料
PDF描述
DS1985-F5 16-kbit Add-Only iButton
DS1985-F3 16-kbit Add-Only iButton
DS1990P Analog IC
DS1990R Analog IC
DS1991L Analog IC
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
DS1985+F3 制造商:Maxim Integrated Products 功能描述:ADD-O IBTN 16KB, F3 (GENERIC) LFREE - Rail/Tube
DS1985+F5 制造商:Maxim Integrated Products 功能描述:ADD-O IBTN 16KB, F5 (GENERIC) LFREE - Rail/Tube
DS1985-F3 功能描述:iButton RoHS:否 存儲(chǔ)類型:SRAM 存儲(chǔ)容量:512 B 組織: 工作電源電壓:3 V to 5.25 V 接口類型:1-Wire 最大工作溫度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封裝 / 箱體:F5 MicroCan 制造商:Maxim Integrated
DS1985-F3# 功能描述:iButton RoHS:否 存儲(chǔ)類型:SRAM 存儲(chǔ)容量:512 B 組織: 工作電源電壓:3 V to 5.25 V 接口類型:1-Wire 最大工作溫度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封裝 / 箱體:F5 MicroCan 制造商:Maxim Integrated
DS1985-F3+ 功能描述:iButton 16Kb Add-Only iButton RoHS:否 存儲(chǔ)類型:SRAM 存儲(chǔ)容量:512 B 組織: 工作電源電壓:3 V to 5.25 V 接口類型:1-Wire 最大工作溫度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封裝 / 箱體:F5 MicroCan 制造商:Maxim Integrated
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