DS1904L-F5 datasheet, PDF - EEWORLD Datasheet

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DS1904L-F5: DescriptionReal Time Clock, 0 Timer(s), CMOS, MEDB2, MICROCAN-2; CategoryThe embedded processor and controller Microcontrollers and processors; File Size71KB，12 Pages; ManufacturerDALLAS; Websitehttp://www.dalsemi.com

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DS1904L-F5 Overview

Real Time Clock, 0 Timer(s), CMOS, MEDB2, MICROCAN-2

DS1904L-F5 Parametric

Parameter Name	Attribute value
Maker	DALLAS
package instruction	MICROCAN-2
Reach Compliance Code	unknown
Information access methods	SERIAL, 1-WIRE
JESD-30 code	O-MEDB-N2
Number of terminals	2
Number of timers
Maximum operating temperature	70 °C
Minimum operating temperature	-40 °C
Package body material	METAL
Package shape	ROUND
Package form	DISK BUTTON
Certification status	Not Qualified
Maximum supply voltage	6 V
Minimum supply voltage	2.8 V
Nominal supply voltage	3.3 V
surface mount	YES
technology	CMOS
Temperature level	OTHER
Terminal form	NO LEAD
Terminal location	END
uPs/uCs/peripheral integrated circuit type	TIMER, REAL TIME CLOCK

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PRELIMINARY

DS1904

RTC iButton

www.iButton.com

SPECIAL FEATURES

Real-Time Clock/calendar in binary format

Uses the same binary time/date representation

as the DS1994 but with 1 second resolution

Clock accuracy is better than

2 minutes per

month at 25°C

Operating temperature range from -40°C to

+70°C

Over 10 years of operation

Presence detector acknowledges when reader

first applies voltage

Meets UL#913 (4th Edit.); Intrinsically Safe

Apparatus, Approved under Entity Concept

for use in Class I, Division 1, Group A, B, C

and D Locations (application pending)

F5 MicroCan



5.89

0.36

0.51

COMMON iButton FEATURES

Unique, factory–lasered and tested 64-bit

registration number (8-bit family code + 48-

bit serial number + 8-bit CRC tester) assures

absolute traceability because no two parts are

alike

Multidrop controller for MicroLAN

Digital identification and information by

momentary contact

Chip-based data carrier compactly stores in-

formation

Data can be accessed while affixed to object

Economically communicates to host with a

single digital signal at 16.3k bits per second

Standard 16 mm diameter and 1-Wire proto-

col ensure compatibility with iButton Device

family

Button shape is self-aligning with cup-shaped

probes

Durable stainless steel case engraved with

registration number withstands harsh envi-

ronments

Easily affixed with self-stick adhesive back-

ing, latched by its flange, or locked with a

ring pressed onto its rim

16.25

YYWW REGISTERED RR

17.35

000000FBC52B

DATA

GROUND

All dimensions are shown in millimeters

ORDERING INFORMATION

DS1904L-F5

F5 MicroCan

EXAMPLES OF ACCESSORIES

DS9096P

DS9101

DS9093RA

DS9093A

DS9092

Self-Stick Adhesive Pad

Multi-Purpose Clip

Mounting Lock Ring

Snap-In Fob

iButton Probe

iButton DESCRIPTION

The DS1904 RTC iButton is a rugged real-time clock module that can be accessed with minimal

hardware. Data is transferred serially via the 1-Wire protocol, which requires only a single data lead and a

ground return. The DS1904 contains a unique 64-bit factory-lasered ROM and a real-time clock/calendar

implemented as a binary counter. The durable MicroCan package is highly resistant to environmental

1 of 12

022400

DS1904

hazards such as dirt, moisture, and shock. Accessories permit the DS1904 to be mounted on almost any

surface including printed circuit boards and plastic key fobs. The DS1904 adds functions such as

calendar, time and date stamp, stopwatch, hour meter, interval timer, and logbook to any type of

electronic device or embedded application that uses a microcontroller.

OVERVIEW

The DS1904 has two main data components: 1) 64-bit lasered ROM, and 2) real-time clock counter

(Figure 1). The real-time clock utilizes an on-chip oscillator that is connected to a 32.768 kHz crystal.

The hierarchical structure of the 1-Wire protocol is shown in Figure 2. The bus master must first provide

one of four ROM function commands: 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM.

The protocol for these ROM functions is described in Figure 7. After a ROM function command is

successfully executed, the real-time clock functions become accessible and the master may then provide

one of the real-time clock function commands. The protocol for these commands is described in Figure 5.

All data is read and written least significant bit first.

BLOCK DIAGRAM

Figure 1

LID

CONTACT

DATA

ROM

FUNCTION

CONTROL

64-BIT

LASERED

ROM

CLOCK

FUNCTION

CONTROL

READ/WRITE BUFFER

LITHIUM

1 Hz

RTC COUNTER (32-BIT)

OSCILLATOR

CONTROL

32.768 kHz

OSCILLATOR

DIVIDER

64-BIT LASERED ROM

Each DS1904 contains a unique ROM code that is 64 bits long. The first eight bits are a 1-Wire family

code. The next 48 bits are a unique serial number. The last eight bits are a CRC of the first 56 bits. (See

Figure 3.) The 1-Wire CRC is generated using a polynomial generator consisting of a shift register and

XOR gates as shown in Figure 4. The polynomial is X

+ X

+ 1. Additional information about the

Dallas Semiconductor 1-Wire Cyclic Redundancy Check is available in the Book of DS19xx iButton

Standards. The shift register bits are initialized to zero. Then starting with the least significant bit of the

family code, one bit at a time is shifted in. After the 8th bit of the family code has been entered, then the

serial number is entered. After the 48th bit of the serial number has been entered, the shift register

contains the CRC value. Shifting in the eight bits of CRC should return the shift register to all zeros. The

64-bit ROM and ROM Function Control section allow the DS1904 to operate as a 1-Wire device and

follow the 1-Wire protocol detailed in the section "1-Wire Bus System".

2 of 12

DS1904

TIMEKEEPING

A 32.768 kHz crystal oscillator is used as the time base for the real-time clock counter. The oscillator can

be turned on or off under software control. The oscillator must be on for the real time clock to function.

The real-time clock counter is double buffered. This allows the master to read time without the data

changing while it is being read. To accomplish this, a snapshot of the counter data is transferred to a

read/write buffer, which the user accesses.

DEVICE CONTROL BYTE

The on/off control of the 32.768 kHz crystal oscillator is done through the device control byte. This byte

can be read and written through the Clock Function commands.

Device Control Byte

Bit 0 - 1

OSC

No function

Bits 0 and 1 are hard-wired to read all 0’s.

Bit 2 - 3

OSC

Oscillator Enable/Disable

These bits control/report whether the 32.768 kHz crystal oscillator is running. If the oscillator is running,

both OSC bits will read 1. If the oscillator is turned off these bits will all read 0. When writing the device

control byte both occurrences of the OSC bit should have identical data. Otherwise the value in bit ad-

dress 3 (bold) takes precedence.

Bit 4 - 7

General-purpose user flags

These non-volatile bits have no particular function within the chip. They can be read and written under

the control of the application software.

REAL-TIME CLOCK

The real-time clock is a 32-bit binary counter. It is incremented once per second. The real-time clock can

accumulate 136 years of seconds before rolling over. Time/date is represented by the number of seconds

since a reference point, which is determined by the user. For example, 12:00 a.m., January 1, 1970 could

be a reference point.

CLOCK FUNCTION COMMANDS

The “Clock Function Flow Chart” (Figure 5) describes the protocols necessary for accessing the real-time

clock. With only four bytes of real-time clock and one control byte the DS1904 does not provide random

access. Reading and writing always starts with the device control byte followed by the least significant

byte of the time data.

4 of 12

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