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DS1501/DS1511
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CONTROL REGISTERS
The controls and status information for the features offered by the DS1501/DS1511 are maintained in the
following register bits.
EOSC
- Oscillator Start/Stop Bit (05H bit 7)
This bit is used to turn the oscillator on and off.
"1" - oscillator off
"0" - oscillator on
The oscillator is automatically turned on by the internal Power on Reset when power is applied and Vcc
rises above the Power-fail Voltage.
E32K
- Enable 32.768kHz Output (05H bit 6)
This bit, when written to a "0", will enable the 32.768 kHz oscillator frequency to be output on the SQW
pin if the oscillator is running. This bit is automatically cleared to a logic “0” to by the internal Power on
Reset when power is applied and Vcc rises above the Power-fail Voltage.
BB32 - Battery Backup 32kHz Enable Bit (05H bit 5)
When the BB32 bit is written to a "1", it will enable a 32kHz signal to be output on the SQW pin while
the part is in battery backup mode if voltage is applied to VBAUX.
AM1-AM4 - Alarm Mask Bits (08H bit 7; 09H bit 7; 0AH bit 7; 0BH bit 7)
Bit 7 of registers 08h to 0Bh contains an alarm mask bit: AM1 to AM4. These bits, in conjunction with
the TIE described later, allow the IRQ output to be activated for a matched alarm condition.
The alarm can be programmed to activate on a specific day of the month, day of the week, or repeat every
day, hour, minute, or second. Table 3 shows the possible settings for AM1 - AM4 and the resulting alarm
rates. Configurations not listed in the table default to the once per second mode to notify the user of an
incorrect alarm setting.
DY/DT - Day/Date Bit (0BH bit 6)
The DY/DT bit controls whether the alarm value stored in bits 0 to 5 of 0BH reflects the day of the week
or the date of the month. If DY/DT is written to a "0", the alarm will be the result of a match with the
date of the month. If DY/DT is written to a "1", the alarm will be the result of a match with the day of the
week.
BLF1 - Valid RAM and Time Bit 1 (0EH bit 7)
BLF2 - Valid RAM and Time Bit 2 (0EH bit 6)
These status bits gives the condition of any batteries attached to the VBAT or VBAUX pins. The
DS1501/DS1511 constantly monitors the battery voltage of the back-up battery sources (VBAT and
VBAUX). The BLF1 and BLF2 bits will be set to a "1" if the battery voltage on VBAT and VBAUX are less
than 2.5V (typical), otherwise BLF1 and BLF2 bits will be a "0". BLF1 reflects the condition of VBAT
with BLF2 reflecting VBAUX. If either bit is read as a "1", the voltage on the respective pin is inadequate
to maintain the RAM memory or clock functions.
PRS - PAB Reset Select Bit (0EH bit 5)
When set to a "0" the PWR pin will be set hi-Z when the DS1501/DS1511 goes into power fail. When set
to a "1", the PWR pin will remain active upon entering power fail.