Electronic Components Datasheet Search
  English  ▼
ALLDATASHEET.COM

X  

DS1985 Datasheet(PDF) 5 Page - Maxim Integrated Products

Part # DS1985
Description  16Kb Add-Only iButton
Download  26 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  MAXIM [Maxim Integrated Products]
Direct Link  https://www.maximintegrated.com/en.html
Logo MAXIM - Maxim Integrated Products

DS1985 Datasheet(HTML) 5 Page - Maxim Integrated Products

  DS1985 Datasheet HTML 1Page - Maxim Integrated Products DS1985 Datasheet HTML 2Page - Maxim Integrated Products DS1985 Datasheet HTML 3Page - Maxim Integrated Products DS1985 Datasheet HTML 4Page - Maxim Integrated Products DS1985 Datasheet HTML 5Page - Maxim Integrated Products DS1985 Datasheet HTML 6Page - Maxim Integrated Products DS1985 Datasheet HTML 7Page - Maxim Integrated Products DS1985 Datasheet HTML 8Page - Maxim Integrated Products DS1985 Datasheet HTML 9Page - Maxim Integrated Products Next Button
Zoom Inzoom in Zoom Outzoom out
 5 / 26 page
background image
DS1985
5 of 26
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 that 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
that 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.


Similar Part No. - DS1985

ManufacturerPart #DatasheetDescription
logo
Dallas Semiconductor
DS1985 DALLAS-DS1985 Datasheet
440Kb / 25P
   16-kbit Add-Only iButton
DS1985-F3 DALLAS-DS1985-F3 Datasheet
440Kb / 25P
   16-kbit Add-Only iButton
DS1985-F5 DALLAS-DS1985-F5 Datasheet
440Kb / 25P
   16-kbit Add-Only iButton
More results

Similar Description - DS1985

ManufacturerPart #DatasheetDescription
logo
Maxim Integrated Produc...
DS2505 MAXIM-DS2505 Datasheet
603Kb / 24P
   16Kb Add-Only Memory
071107
DS1982 MAXIM-DS1982 Datasheet
695Kb / 24P
   1Kb Add-Only iButton
Rev 8/09
logo
Dallas Semiconductor
DS1985 DALLAS-DS1985 Datasheet
440Kb / 25P
   16-kbit Add-Only iButton
DS1982 DALLAS-DS1982 Datasheet
444Kb / 23P
   1-kbit Add-Only iButton
DS1986 DALLAS-DS1986 Datasheet
548Kb / 27P
   64-kbits Add-Only iButton?
logo
Maxim Integrated Produc...
DS1995 MAXIM-DS1995 Datasheet
45Kb / 2P
   16Kb Memory iButton
Rev 8/09
DS2506 MAXIM-DS2506 Datasheet
898Kb / 25P
   64Kb Add-Only Memory
062100
DS2502 MAXIM-DS2502_11 Datasheet
1Mb / 24P
   1Kb Add-Only Memory
Rev 12/11
logo
Dallas Semiconductor
DS2502-UN DALLAS-DS2502-UN Datasheet
46Kb / 3P
   UniqueWare Add-Only Memory
logo
Maxim Integrated Produc...
DS2502 MAXIM-DS2502_V01 Datasheet
693Kb / 24P
   1Kb Add-Only Memory
2015
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26


Datasheet Download

Go To PDF Page


Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Link Exchange   |   Manufacturer List
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com