DS1500_11 MAXIM [Maxim Integrated Products], DS1500_11 Datasheet - Page 13

• Manufacturer Part Number: DS1500_11
• Description: Y2K Watchdog RTC with Nonvolatile Control
• Manufacturer: MAXIM [Maxim Integrated Products]

SETTING THE CLOCK
It is recommended to halt updates to the external set of double buffered RTC registers when writing to the clock.
The (TE) bit should be used as described above before loading the RTC registers with the desired RTC count (day,
date, and time) in 24-hour BCD format. Setting the (TE) bit to 1 transfers the new values written to the internal RTC
registers and allows normal operation to resume.
CLOCK ACCURACY
A standard 32.768kHz quartz crystal should be directly connected to the DS1500 X1 and X2 oscillator pins. The
crystal selected for use should have a specified load capacitance (C
select (CS) bit set accordingly. For more information about crystal selection and crystal layout considerations, refer
to Application Note 58: Crystal Considerations with Maxim Real-Time Clocks (RTCs). An external 32.768kHz
oscillator can also drive the DS1500. To achieve low-power operation when using an external oscillator, it may be
necessary to connect the X1 pin to the external oscillator signal through a series connection consisting of a resistor
and a capacitor. A typical configuration consists of a 1.0M resistor in series with a 100pF ceramic capacitor. When
using an external oscillator the X2 pin must be left open.
Table 2. Register Map
0 = “0” and are read only.
POWER-UP DEFAULT STATES
These bits are set upon power-up: EOSC = 0, E32K = 0, TIE = 0, KIE = 0, WDE = 0, and WDS = 0.
Note: Unless otherwise specified, the state of the control/RTC/SRAM bits in the DS1500 is not defined upon initial
power application; the DS1500 should be properly configured/defined during initial configuration.
USING THE CLOCK ALARM
The alarm settings and control reside within registers 08h to 0Bh (Table 2). The TIE bit and alarm mask bits AM1 to
AM4 must be set as described below for the IRQ or PWR outputs to be activated for a matched alarm condition.
The alarm functions as long as at least one supply is at a valid level. Note that activating the PWR pin requires the
use of V
ADDRESS
14h-1Fh
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
10h
11h
12h
13h
BAUX
.
EOSC
BLF1
AM1
AM2
AM3
AM4
TE
B7
0
0
0
0
0
Dy/Dt
E32K
BLF2
10 CENTURY
CS
B6
0
0
0
0
0.1 Second
10 Second
10 YEAR
10 Seconds
10 Seconds
10 Minutes
10 Minutes
BB32
BME
PRS
B5
0
10 Hours
10 Hours
10 Date
10 Date
Extended RAM Address
Extended RAM Data
10 MO
PAB
TPE
B4
Reserved
Reserved
Reserved
0
DATA
TDF
13 of 20
TIE
B3
0
KSF
B2
0.01 Second
KIE
Day/Date
Seconds
Seconds
Minutes
Century
Minutes
Second
Month
Hour
Date
Year
Hour
B1
WDF
WDE
Day
L
) of either 6pF or 12.5pF, and the crystal
IRQF
WDS
B0
RAM Address LSB
Alarm Day/Date
Alarm Seconds
Alarm Minutes
Alarm Hours
FUNCTION
RAM Data
Watchdog
Watchdog
Control A
Control B
Seconds
Minutes
Century
Month
Hours
Date
Year
Day
1–7/1–31
RANGE
00–FF
00–FF
00–59
00–59
00–23
01–31
01–12
00–99
00–39
00–59
00–59
00–23
00–99
00–99
BCD
1–7