Ubuntu Manpage: DS2502 - Add-Only Memory (1 kBit)

Provided by: owfs-doc_3.2p4+dfsg1-4.3build2_all

NAME

       DS2502 - Add-Only Memory (1 kBit)

       DS2502-E48, DS2502-UNW
              - 48-bit Node Address Chip, UniqueWare Add-Only Memory (1 kBit)

       DS1982, DS1982U
              - Add-Only iButton (1 kBit), UniqueWare iButton (1 kBit)

SYNOPSIS

       EPROM add-only memory.

       09  [.]XXXXXXXXXXXX[XX][/[ memory | pages/page.[0-3|ALL] | address | crc8 | id | locator |
       r_address | r_id | r_locator | type ]]

       89 [.]XXXXXXXXXXXX[XX][/[ mac_e | mac_fw |  memory  |  pages/page.[0-3|ALL]  |  project  |
       address | crc8 | id | locator | r_address | r_id | r_locator | type ]]

FAMILY CODE

       09     DS2502 DS1982

       89     DS2502-UNW DS2502-E48 DS1982U

SPECIAL PROPERTIES

   mac_e mac_fw
       read-only, binary
       64 bit or 80 bit media access control number. Unique, and unrelated to the 1-wire address.
       It is apparently used for ethernet or FireWire addressing, respectively.

   memory
       read-write, binary
       128 bytes of memory. Initially all bits are set to 1. Writing zero permanently alters  the
       memory.

   pages/page.0 ... pages/page.3 pages/page.ALL
       read-write, yes-no
       Memory  is  split  into  4 pages of 32 bytes each.  ALL is an aggregate of the pages. Each
       page is accessed sequentially.

   project
       read-only, binary
       32 bit project id.  Constant  0x0000  for  ethernet  and   0x00001128  for  firewire.  See
       Datasheets.

STANDARD PROPERTIES

address
r_address
read-only, ascii
The entire 64-bit unique ID. Given as upper case hexadecimal digits (0-9A-F).
address starts with the family code
r address is the address in reverse order, which is often used in other applications and
labeling.

crc8
read-only, ascii
The 8-bit error correction portion. Uses cyclic redundancy check. Computed from the
preceding 56 bits of the unique ID number. Given as upper case hexadecimal digits (0-9A-
F).

family
read-only, ascii
The 8-bit family code. Unique to each type of device. Given as upper case hexadecimal
digits (0-9A-F).

id
r_id
read-only, ascii
The 48-bit middle portion of the unique ID number. Does not include the family code or
CRC. Given as upper case hexadecimal digits (0-9A-F).
r id is the id in reverse order, which is often used in other applications and labeling.

locator
r_locator
read-only, ascii
Uses an extension of the 1-wire design from iButtonLink company that associated 1-wire
physical connections with a unique 1-wire code. If the connection is behind a Link Locator
the locator will show a unique 8-byte number (16 character hexadecimal) starting with
family code FE.
If no Link Locator is between the device and the master, the locator field will be all FF.
r locator is the locator in reverse order.

present (DEPRECATED)
read-only, yes-no
Is the device currently present on the 1-wire bus?

type
read-only, ascii
Part name assigned by Dallas Semi. E.g. DS2401 Alternative packaging (iButton vs chip)
will not be distiguished.

ALARMS

       None.

DESCRIPTION

1-Wire
1-wire is a wiring protocol and series of devices designed and manufactured by Dallas
Semiconductor, Inc. The bus is a low-power low-speed low-connector scheme where the data
line can also provide power.

Each device is uniquely and unalterably numbered during manufacture. There are a wide
variety of devices, including memory, sensors (humidity, temperature, voltage, contact,
current), switches, timers and data loggers. More complex devices (like thermocouple
sensors) can be built with these basic devices. There are also 1-wire devices that have
encryption included.

The 1-wire scheme uses a single bus master and multiple slaves on the same wire. The bus
master initiates all communication. The slaves can be individually discovered and
addressed using their unique ID.

Bus masters come in a variety of configurations including serial, parallel, i2c, network
or USB adapters.

OWFS design
OWFS is a suite of programs that designed to make the 1-wire bus and its devices easily
accessible. The underlying principle is to create a virtual filesystem, with the unique ID
being the directory, and the individual properties of the device are represented as simple
files that can be read and written.

Details of the individual slave or master design are hidden behind a consistent interface.
The goal is to provide an easy set of tools for a software designer to create monitoring
or control applications. There are some performance enhancements in the implementation,
including data caching, parallel access to bus masters, and aggregation of device
communication. Still the fundamental goal has been ease of use, flexibility and
correctness rather than speed.

DS2502 DS1982
The DS2502 (3) is used for write-once incremental storage. It's main advantage is for
audit trails (i.e. a digital purse).

The DS2502-E48 and DS2502-UNW are some of the UniqueWare class of devices. Some of the
memory was preprogramed at the factory. See the datasheet for specifics. The DS2502 ,
DS2505 , and DS2506 differ in their function by the amount of on-board memory they
possess. (The internal protocols are slightly different, but the OWFS system handles this
automatically.

ADDRESSING

       All 1-wire devices are factory assigned a unique 64-bit address. This address  is  of  the
       form:

       Family Code
              8 bits

       Address
              48 bits

       CRC    8 bits

       Addressing under OWFS is in hexadecimal, of form:

              01.123456789ABC

       where 01 is an example 8-bit family code, and 12345678ABC is an example 48 bit address.

       The dot is optional, and the CRC code can included. If included, it must be correct.

DATASHEET

       http://pdfserv.maxim-ic.com/en/ds/DS2502.pdf
       http://pdfserv.maxim-ic.com/en/ds/DS2502-E48.pdf
       http://pdfserv.maxim-ic.com/en/ds/DS2502-UNW-DS2506S-UNW.pdf
       http://pdfserv.maxim-ic.com/en/ds/DS1982-F3-DS1982-F5.pdf
       http://pdfserv.maxim-ic.com/en/ds/DS1982U-DS1986U.pdf

AVAILABILITY

       http://www.owfs.org

AUTHOR

       Paul Alfille (paul.alfille@gmail.com)