DS1921G Просмотр технического описания (PDF) - Maxim Integrated

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производитель

DS1921G

Thermochron iButton

Maxim Integrated 

Thermochron iButton

ADDRESS

0210h

0211h

0212h

0213h

0214h

0215h

0216h

0217h

0218h

0219h

021Ah

021Bh

021Ch

021Dh

021Eh

021Fh

BIT 7

TCB

BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1

(No function, reads 00h)

Temperature Read-Out (Forced Conversion)

Low Byte

High Byte

MEMCLR MIP

SIP

0

TLF

THF

Minutes

Hours

Date

Month

Year

Low Byte

Center Byte

High Byte

Low Byte

Center Byte

High Byte

BIT 0

TAF

FUNCTION

—

Temperature

Mission Start

Delay

Status

ACCESS*

R

R**

R

R**

R/W R/W**

R/W R/W

Mission

Timestamp

R

R

Mission

Samples

R

R

Counter

Device

Samples

R

R

Counter

*The left entry in the ACCESS column is valid between missions. The right entry shows the applicable access mode while a

mission is in progress.

**While a mission is in progress, these addresses can be read. The first attempt to write to these registers (even read-only

ones), however, ends the mission and overwrites selected writable registers.

Figure 6. Register Pages Map (continued)

Detailed Register Descriptions

Timekeeping

The RTC/alarm and calendar information is accessed

by reading/writing the appropriate bytes in the register

page, address 0200h to 0206h. Note that some bits are

set to 0. These bits always read 0 regardless of how

they are written. The contents of the time, calendar, and

alarm registers are in the binary-coded decimal (BCD)

format.

RTC/Calendar

The RTC of the DS1921G can run in either 12hr or 24hr

mode. Bit 6 of the Hours register (address 0202h) is

defined as the 12hr or 24hr mode select bit. When high,

the 12hr mode is selected. In the 12hr mode, bit 5 is the

AM/PM bit with logic 1 being PM. In the 24hr mode, bit

5 is the 20hr bit (20hr to 23hr).

To distinguish between the days of the week, the

DS1921G includes a counter with a range from 1 to 7.

The assignment of a counter value to the day of week is

arbitrary. Typically, the number 1 is assigned to a

Sunday (U.S. standard) or to a Monday (European stan-

dard).

The calendar logic is designed to automatically com-

pensate for leap years. For every year value that is

either 00 or a multiple of four, the device adds a 29th of

February. This works correctly up to (but not including)

the year 2100.

The DS1921G is Y2K compliant. Bit 7 (CENT) of the

Months register at address 0205h serves as a century

flag. When the Year register rolls over from 99 to 00, the

century flag toggles. It is recommended to write the

century bit to a 1 when setting the RTC to a time/date

between the years 2000 and 2099.

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