DS1307 Просмотр технического описания (PDF) - Dallas Semiconductor -> Maxim Integrated

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DS1307

64 x 8 Serial Real-Time Clock

Dallas Semiconductor -> Maxim Integrated 

DS1307

CLOCK ACCURACY

The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match

between the capacitive load of the oscillator circuit and the capacitive load for which the crystal was

trimmed. Additional error will be added by crystal frequency drift caused by temperature shifts. External

circuit noise coupled into the oscillator circuit may result in the clock running fast. See Application Note

58, “Crystal Considerations with Dallas Real-Time Clocks” for detailed information.

Please review Application Note 95, “Interfacing the DS1307 with a 8051-Compatible Microcontroller”

for additional information.

RTC AND RAM ADDRESS MAP

The address map for the RTC and RAM registers of the DS1307 is shown in Figure 2. The RTC registers

are located in address locations 00h to 07h. The RAM registers are located in address locations 08h to

3Fh. During a multi-byte access, when the address pointer reaches 3Fh, the end of RAM space, it wraps

around to location 00h, the beginning of the clock space.

DS1307 ADDRESS MAP Figure 2

00H

SECONDS

MINUTES

HOURS

DAY

DATE

MONTH

YEAR

07H

CONTROL

08H

RAM

56 x 8

3FH

CLOCK AND CALENDAR

The time and calendar information is obtained by reading the appropriate register bytes. The RTC

registers are illustrated in Figure 3. The time and calendar are set or initialized by writing the appropriate

register bytes. The contents of the time and calendar registers are in the BCD format. Bit 7 of register 0

is the clock halt (CH) bit. When this bit is set to a 1, the oscillator is disabled. When cleared to a 0, the

oscillator is enabled.

Please note that the initial power-on state of all registers is not defined. Therefore, it is important

to enable the oscillator (CH bit = 0) during initial configuration.

The DS1307 can be run in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the

12- or 24-hour mode select bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is

the AM/PM bit with logic high being PM. In the 24-hour mode, bit 5 is the second 10 hour bit (20-

23 hours).

On a 2-wire START, the current time is transferred to a second set of registers. The time information is

read from these secondary registers, while the clock may continue to run. This eliminates the need to re-

read the registers in case of an update of the main registers during a read.

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