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NAME

       DS1825 - Programmable Resolution 1-Wire Digital Thermometer with ID

       MAX31826
              - Digital Temperature Sensor with 1Kb Lockable EEPROM

       MAX31850 MAX31851
              - Cold-Junction Compensated Thermocouple

SYNOPSIS

   Thermometer with hardware address pins (DS1825)
       3B  [.]XXXXXXXXXXXX[XX][/[  fasttemp  |  temperature  |  temperature9  |  temperature10  |
       temperature11 | temperature12 | power | prog_addr | temphigh | templow | address | crc8  |
       id | locator | r_address | r_id | r_locator | type ]]

   Digital Temperature Sensor with 1Kb Lockable EEPROM (MAX31826)
       3B [.]XXXXXXXXXXXX[XX][/[ temperature | power | memory | pages/page.[0-15|ALL] | prog_addr
       | address | crc8 | id | locator | r_address | r_id | r_locator | type ]]

   Cold-Junction Compensated Thermocouple (MAX31850 and MAX31851)
       3B [.]XXXXXXXXXXXX[XX][/[ temperature | thermocouple | fault | open_circuit | ground_short
       |  vdd_short  |  power  |  prog_addr  | address | crc8 | id | locator | r_address | r_id |
       r_locator | type ]]

FAMILY CODE

       3B

SPECIAL PROPERTIES

   power
       read-only,yes-no
       Is the chip powered externally (=1) or from the parasitically from the data bus (=0)?

   prog_addr
       read-only, 0-15
       A distiguishing feature of the DS1825 (3) is the ability  to  set  hardware  pins  for  an
       address  (0-15).  This  is  an alternative to the unique 64-bit address that is set in the
       factory.

   temperature
       read-only, floating point
       Measured temperature with 12 bit resolution.

       For the MAX31850 MAX 31851 this is the cold-junction temperature -- the temperature at the
       chip. See thermocouple

   temperature9 temperature10 temperature11 temperature12
       read-only, floating point ( DS1825 only)

       Measured  temperature  at  9  to  12  bit  resolution.  There is a tradeoff of time versus
       accuracy in the temperature measurement.

       The MAX31826 MAX31850 MAX31851 measure all temperatures  at  12  bit  resoltion  and  will
       return that resolution to all the possible temperature properties.

   fasttemp
       read-only, floating point
       Equivalent to temperature9

   thermocouple
       read-only, floating point ( MAX31850 MAX31851 only)

       Measured  temperature  of  the thermocouple at 16bit resolution. Cold-junction temperature
       compensated.

       The actual thermocouple  type  used  is  set  by  the  selected  chip  type,  and  is  not
       discoverable in software.

TEMPERATURE ALARM LIMITS

       When  the device exceeds either temphigh or templow temperature threshold the device is in
       the alarm state, and will appear in the alarm directory. This provides an easy way to poll
       for  temperatures  that  are  unsafe, especially if simultaneous temperature conversion is
       done.

       Units for the temperature alarms are in the  same  temperature  scale  that  was  set  for
       temperature measurements.

       Temperature  thresholds  are stored in non-volatile memory and persist until changed, even
       if power is lost.

   temphigh
       read-write, integer
       Shows or sets the lower limit for the high temperature alarm state.

   templow
       read-write, integer
       Shows or sets the upper limit for the low temperature alarm state.

       The MAX31826 does NOT have temperature thresholds and temperature alarm.

MEMORY

       Only the MAX31826 supports memory functions.

   pages/page.0 .. pages/page.15 pages/page.ALL
       read/write, binary
       EEPROM memory pages of 8 bytes each. See the datasheet about locking contents.

   memory
       read/write, binary
       EEPROM memory of 128 bytes. See the datasheet about locking contents.

FAULT REPORTING

       Only the MAX31850 MAX31851 supports fault reporting.

   fault
       read-only, yes-no
       Fault in last thermocouple conversion

   open_circuit
       read-only, yes-no
       Thermocouple leads disconnected.

   ground_short
       read-only, yes-no
       Thermocouple lead shorted to ground.

   vdd_short
       read-only, yes-no
       Thermocouple lead shorted to supply voltage.

STANDARD PROPERTIES

   address
   r_address
       read-only, ascii
       The entire 64-bit unique ID. Given as upper case hexidecimal 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 hexidecimal  digits  (0-9A-
       F).

   family
       read-only, ascii
       The  8-bit  family  code.  Unique  to each type of device. Given as upper case hexidecimal
       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 hexidecimal 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 hexidecimal) 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.

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  fundemental  goal  has  been  ease  of  use,  flexibility  and
       correctness rather than speed.

   DS1825
       The DS1825 (3) is one of several available 1-wire temperature  sensors.  Alternatives  are
       the  DS18S20  (3), DS18B20 (3), and DS1822 (3) as well as temperature/voltage measurements
       in the DS2436 (3) and DS2438 (3).  For truly versatile temperature measurements,  see  the
       protean DS1921 (3) Thermachron (3).

       The  DS1825  (3)  can  select  between  4  resolutionsspanning  the  fastest/roughest  and
       slowest/best.

   MAX31826
       The MAX31826 shares a family code with the DS1825 but  has  differences  in  some  of  its
       functions.

       The  MAX31826  has 128 btes of EEPROM memory (as 16 pages of 8 bytes) while the DS1825 has
       no memory available.

       The MAX31826 measures temperature at 12 bit resolution as  fast  as  the  DS1825's  lowest
       resolution  (and  always  uses 12-bit resolution). On the other hand it has no temperature
       thresholds or alarm function.

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 hexidecimal, 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.

       Both  the  MAX31826  and the DS1825 allow hardware selection of part of the address, which
       can assist selecting between chips is some circuit designs.

DATASHEET

       DS1825 http://pdfserv.maxim-ic.com/en/ds/DS1825.pdf

       MAX31826
              http://datasheets.maxim-ic.com/en/ds/MAX31826.pdf

SEE ALSO

   Programs
       owfs (1) owhttpd (1) owftpd (1) owserver (1) owdir (1) owread (1)  owwrite  (1)  owpresent
       (1) owtap (1)

   Configuration and testing
       owfs (5) owtap (1) owmon (1)

   Language bindings
       owtcl (3) owperl (3) owcapi (3)

   Clocks
       DS1427 (3) DS1904(3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3) DS2417 (3)

   ID
       DS2401 (3) DS2411 (3) DS1990A (3)

   Memory
       DS1982  (3)  DS1985  (3) DS1986 (3) DS1991 (3) DS1992 (3) DS1993 (3) DS1995 (3) DS1996 (3)
       DS2430A (3) DS2431 (3) DS2433 (3) DS2502 (3) DS2506 (3) DS28E04 (3) DS28EC20 (3)

   Switches
       DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3) DS28EA00 (3)

   Temperature
       DS1822 (3) DS1825 (3) DS1820 (3) DS18B20 (3) DS18S20 (3) DS1920 (3) DS1921 (3) DS1821  (3)
       DS28EA00  (3)  DS28E04  (3)  EDS0064  (3)  EDS0065 (3) EDS0066 (3) EDS0067 (3) EDS0068 (3)
       EDS0071 (3) EDS0072 (3) MAX31826 (3)

   Humidity
       DS1922 (3) DS2438 (3) EDS0065 (3) EDS0068 (3)

   Voltage
       DS2450 (3)

   Resistance
       DS2890 (3)

   Multifunction (current, voltage, temperature)
       DS2436 (3) DS2437 (3) DS2438 (3) DS2751 (3) DS2755 (3) DS2756 (3) DS2760  (3)  DS2770  (3)
       DS2780 (3) DS2781 (3) DS2788 (3) DS2784 (3)

   Counter
       DS2423 (3)

   LCD Screen
       LCD (3) DS2408 (3)

   Crypto
       DS1977 (3)

   Pressure
       DS2406 (3) TAI8570 EDS0066 (3) EDS0068 (3)

   Moisture
       EEEF (3) DS2438 (3)

AVAILABILITY

       http://www.owfs.org

AUTHOR

       Paul Alfille (paul.alfille@gmail.com)