NAME

DS28E04 - 1-Wire EEPROM chip (4096-bit) with seven address inputs

SYNOPSIS

4096-bit EEPROM, 2 port switch

FAMILY CODE

SPECIAL PROPERTIES

latch.0 latch.1 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 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 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 DS28E04 powered parasitically (=0) or separately on the Vcc pin (=1)?

sensed.0 sensed.1 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.

0: PIO powers up 0
1: 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 always 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:

133: Responds on Conditional Search when latch.1 or latch.0 are set to 1.
222: Responds on Conditional Search when sensed.1 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 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

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 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.

DS28E04

The DS28E04 (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 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/DS28E04.pdf

AVAILABILITY

http://www.owfs.org

AUTHOR

Paul Alfille (paul.alfille@gmail.com)