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DS2417

1-Wire Time Chip with Interrupt

Maxim Integrated 

Bit 4 - 6 IS Interval Select

These bits determine the time between interrupt pulses. The values available are shown below.

IS2 IS1 IS0

Interrupt Interval

0

0

0 1s

0

0

1 4s

0

1

0 32s = 0.53 min.

0

1

1 64s = 1.07 min.

1

0

0 2048s = 34.13 min.

1

0

1 4096s = 68.27 min.

1

1

0 65536s = 18.20 hours

1

1

1 131072s = 36.41 hours

DS2417

Bit 7 IE Interrupt Enable

This bit controls whether the interrupt pulse will be generated at the selected interval. To enable interrupts

this bit needs to be 1.

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 DS2417 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.

READ CLOCK [66h]

The read clock command is used to read the device control byte and the contents of the real-time clock

counter. After having received the most significant bit of the command code the device copies the actual

contents of the real-time clock counter to the read/write buffer. Now, the bus master reads data beginning

with the device control byte followed by the least significant byte through the most significant byte of the

real-time clock. After this the bus master may continue reading from the DS2417. The data received will be

the same as in the first pass through the command flow. The read clock command can be ended at any point

by issuing a Reset Pulse.

WRITE CLOCK [99h]

The write clock command is used to set the real-time clock counter and to write the device control byte.

After issuing the command, the bus master writes first the device control byte, which becomes immediately

effective. After this the bus master sends the least significant byte through the most significant byte to be

written to the real-time clock counter. The new time data is copied from the read/write buffer to the real-time

clock counter and becomes effective as the bus master generates a reset pulse. If enabled, an interrupt pulse

will be generated either immediately or delayed, depending on the actual time and the selected interval

duration (see Figure 11). If the oscillator is intentionally stopped the real-time clock counter behaves as a

four-byte nonvolatile memory.

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