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Table of Contents

Name

DS2804 - is a 4096-bit, 1-Wire EEPROM chip with seven address inputs

Synopsis

4096-bit EEPROM, 2 port switch

1C [.]XXXXXXXXXXXX[XX][/[ latch.[0-1|ALL|BYTE] | PIO.[0-1|ALL|BYTE] | power | sensed.[0-1|ALL|BYTE] | polarity | por | set_alarm | address | crc8 | id | locator | present | r_address | r_id | r_locator | type ]]

Family Code

1C

Special Properties

latch.0 latch.1.html latch.ALL latch.BYTE

read-write, binary
The 2 pins (PIO) latch a bit when their state changes, either externally, or through a write to the pin.
Reading the latch property indicates that the latch has been set.
Writing any data to ANY latch will reset them all. (This is the hardware design).
ALL is all latch states, accessed simultaneously, comma separated.
BYTE references all channels simultaneously as a single byte. Channel 0 is bit 0.

Pio.0 Pio.1.html Pio.all Pio.byte

read-write, yes-no
State of the open-drain output ( PIO ) pin. 0 = non-conducting = off, 1 = conducting = on.
Writing zero will turn off the switch, non-zero will turn on the switch. Reading the PIO state will return the switch setting. To determine the actual logic level at the switch, refer to the sensed.0 sensed.1.html sensed.ALL sensed.BYTE property.
ALL references all channels simultaneously, comma separated.
BYTE references all channels simultaneously as a single byte. Channel 0 is bit 0.

power

read-only, yes-no
Is the DS2804 powered parasitically (=0) or separately on the Vcc pin (=1)?

sensed.0 sensed.1.html sensed.ALL sensed.BYTE

read-only, yes-no
Logic level at the PIO pin. 0 = ground. 1 = high (~2.4V - 5V ). Really makes sense only if the PIO state is set to zero (off), else will read zero.
ALL references all channels simultaneously, comma separated.
BYTE references all channels simultaneously as a single byte. Channel 0 is bit 0.

polarity

read-only, yes-no
Reports the state of the POL pin. The state of the POL pin specifies whether the PIO pins P0 and P1 power up high or low. The polarity of a pulse generated at a PIO pin is the opposite of the pin’s power-up state.
  1. PIO powers up 0
  2. PIO powers up 1

por

read-write, yes-no
Specifies whether the device has performed power-on reset. This bit can only be cleared to 0 under software control. As long as this bit is 1 the device will allways respond to a conditional search.

set_alarm

read-write, integer unsigned (0-333)
A number consisting of 3 digits XYY, where:
X
select source and logical term
0 PIO OR
1 latch OR
2 PIO AND
3 latch AND
Y
select channel and polarity
0 Unselected (LOW)
1 Unselected (HIGH)
2 Selected LOW
3 Selected HIGH

All digits will be truncated to the 0-3 range. Leading zeroes are optional. Low-order digit is channel 0.

Example:

  1. Responds on Conditional Search when latch.1.html or latch.0 are set to 1.
  2. Responds on Conditional Search when sensed.1.html and sensed.0 are set to 0.
    000 (0)
    Never responds to Conditional Search.

    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 preceeding 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

    read-only, yes-no
    Is the device currently present on the 1-wire bus?
    Note, this means that each hex byte (2 characters) is reversed, not the text string.

    type

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

    Alarms

    Use the set_alarm property to set the alarm triggering criteria.

    Description

    1-Wire

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

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

    The 1-wire bus is accessed via one of a number of serial, parallel or USB adapters.

    OWFS design

    OWFS is a suite of programs that fundementally make the 1-wire bus and its devices easily accessible. The underlying priciple is to create a virtual filesystem, with the unique ID being the directory, and the individual properties of the device files.

    There is optional data caching to improved performance, but possible confusion over stale data.

    Ds2804

    The DS2804 (3) is a memory chip that bends the unique addressing capabilities of the 1-wire design. Some of the ID bits can be assigned by hardware.

    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.

    Datasheet

    http://pdfserv.maxim-ic.com/en/ds/DS2804.pdf

    See Also

    Programs

    owfs (1) owhttpd (1) owftpd (1) owserver (1)

    Language bindings

    owtcl (3) owperl (3)

    Clocks

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

    ID

    DS2401 (3) DS1990A (3)

    Memory

    DS1982 (3) DS1985 (3) DS1986 (3) DS1991 (3) DS1992 (3) DS1993 (3) DS1995 (3) DS1996 (3) DS2431 (3) DS2433 (3) DS2502 (3) DS2506 (3) DS2804 (3)

    Switches

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

    Temperature

    DS1822 (3) DS18B20 (3) DS18S20 (3) DS1920 (3) DS1921 (3) DS1821 (3)

    Humidity

    DS1922 (3)

    Voltage

    DS2450 (3)

    Resistance

    DS2890 (3)

    Multifunction

    DS2436 (3) DS2438 (3) DS2760 (3)

    Counter

    DS2423 (3)

    LCD Screen

    LCD (3) DS2408 (3)

    Crypto

    DS1977 (3)

    Availability

    http://owfs.sourceforge.net

    Author

    Paul Alfille (palfille@earthlink.net)


    Table of Contents

© 2003-4 Paul H. Alfille and The owfs Team
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