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DW01 , One Cell Lithium-ion/Polymer Battery Protection IC
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DS1693
3 Volt/5 Volt Serialized Real Time Clock with NV RAM Control
FEATURES
Incorporates Industry Standard DS1287 PC
Clock Plus Enhanced Features: � +3V or +5V Operation � 64-Bit Silicon Serial Number � 64-Bit Customer Specific ROM or
Additional Serial Number Available � Power Control Circuitry Supports System
Power-On from Date/Time Alarm or Key
Closure � Automatic Battery Backup and Write
Protection to External SRAM � Crystal Select Bit Allows RTC to Operate
with 6pF or 12.5pF Crystal � 114 Bytes User NV RAM � Auxiliary Battery Input
� RAM Clear Input � Century Register � 32kHz Output for Power Management � 32-Bit VCC Powered Elapsed Time Counter � 32-Bit VBAT Powered Elapsed Time Counter � 16-Bit Power Cycle Counter � Compatible with Existing BIOS for Original
DS1287 Functions � Available as IC (DS1689) or Stand-Alone
Module with Embedded Battery and Crystal
(DS1693) � Available in Industrial Temperature
Version � Timekeeping Algorithm Includes Leap Year
Compensation Valid Up to 2100
PIN CONFIGURATIONS
ORDERING INFORMATION
PART TEMP RANGE VOLTAGE (V) PIN-PACKAGE TOP MARK*
DS1689S 0°C to +70°C 3 to 5 28 SO (0.330″) DS1689S
DS1689S+ 0°C to +70°C 3 to 5 28 SO (0.330″) DS1689S
DS1689SN -40°C to +85°C 3 to 5 28 SO (0.330″) DS1689S
DS1689SN+ -40°C to +85°C 3 to 5 28 SO (0.330″) DS1689S
DS1689S/T&R 0°C to +70°C 3 to 5 28 SO (0.330″)/Tape & Reel DS1689S
DS1689S+T&R 0°C to +70°C 3 to 5 28 SO (0.330″)/Tape & Reel DS1689S
DS1689SN/T&R -40°C to +85°C 3 to 5 28 SO (0.330″)/Tape & Reel DS1689S
DS1689SN+T&R -40°C to +85°C 3 to 5 28 SO (0.330″)/Tape & Reel DS1689S
DS1689/DS1693
3V/5V Serialized Real-Time Clocks
with NV RAM Control
Encapsulated DIP
(740 Mils) 13
N.C.
AD0
AD2
AD3
AD4
AD5
AD6
AD7
GND
PWR
CEI
VCCO
SQW
N.C.
IRQ
PSEL
RD
N.C.
WR
ALE
KS
CS
10
11
12
14
N.C.
RCLR
AD1
VBAUX
CEO VCCI
DS16
93 VBAUX
SO
(330 Mils) 13
10
11
12
14
CEI
VCCO
SQW
VBAT
IRQ
PSEL
RD
GND
WR
ALE
KS
CS
CEO
VCCI X2
AD0
AD2
AD3
AD4
AD5
AD6
AD7
GND
PWR
RCLR
AD1
DS16
89
DS1689/DS1693
PIN DESCRIPTION
PIN
SO EDIP NAME FUNCTION 1 1 VBAUX
Auxiliary Battery Supply. Auxiliary battery input required for
kickstart and wake-up features. This input also supports
clock/calendar and External NV RAM if VBAT is at lower voltage or
is not present. A standard +3V lithium cell or other energy source
can be used. Battery voltage must be held between +2.5V and +3.7V
for proper operation. If VBAUX is not going to be used it should be
grounded and auxiliary battery enable bit bank 1, register 4BH,
should = 0.
2, 3 — X1, X2
Connections for Standard 32.768kHz Quartz Crystal. For greatest
accuracy, the DS1689 must be used with a crystal that has a
specified load capacitance of either 6pF or 12.5pF. The crystal select
(CS) bit in Extended Control Register 4B is used to select operation
with a 6pF or 12.5pF crystal. The crystal is attached directly to the
X1 and X2 pins. There is no need for external capacitors or resistors.
Note: X1 and X2 are very high-impedance nodes. It is recommended
that they and the crystal by guard-ringed with ground and that high-
frequency signals be kept away from the crystal area.
For more information on crystal selection and crystal layout
considerations, refer to Application Note 58: Crystal Considerations
with Dallas Real Time Clocks. The DS1689 can also be driven by an
external 32.768kHz oscillator. In this configuration, the X1 pin is
connected to the external oscillator signal and the X2 pin is floated.
4 4 RCLR
Active-Low RAM Clear Input. If enabled by software, taking RCLR
low will result in the clearing of the 114 bytes of user RAM. When
enabled, RCLR can be activated whether or not VCC is present.
5–12 5–12 AD0–AD7
Multiplexed Address/Data Bus. Multiplexed buses save pins because
address information and data information time-share the same signal
paths. The addresses are present during the first portion of the bus
cycle and the same pins and signal paths are used for data in the
second portion of the cycle. Address/data multiplexing does not slow
the access time of the DS1689 since the bus change from address to
data occurs during the internal RAM access time. Addresses must be
valid prior to the latter portion of ALE, at which time the
DS1689/DS1693 latches the address. Valid write data must be
present and held stable during the latter portion of the WR pulse. In a
read cycle, the DS1689/
DS1693 outputs 8 bits of data during the latter portion of the RD
pulse. The read cycle is terminated and the bus returns to a high
impedance state as RD transitions high. The address/data bus also
serves as a bidirectional data path for the external extended RAM.
PIN
SO EDIP NAME FUNCTION 13 13 PWR
Active-Low Power-On Interrupt Output. The PWR pin is intended
for use as an on/off control for the system power. With VCC voltage
removed from the DS1689/DS1693, PWR may be automatically
activated from a kickstart input via the KS pin or from a wake-up
interrupt. Once the system is powered on, the state of PWR can be
controlled via bits in the Dallas registers.
14, 19 14 GND Ground. DC power is provided to the device on this pin.
15 15 KS
Active-Low Kickstart Input. When VCC is removed from the
DS1689/DS1693, the system can be powered on in response to an
active low transition on the KS pin, as might be generated from a
key closure. VBAUX must be present and auxiliary battery enable bit
(ABE) must be set to 1 if the kickstart function is used, and the KS
pin must be pulled up to the VBAUX supply. While VCC is applied, the
KS pin can be used as an interrupt input.
16 16 CS
Active-Low Chip Select Input. This signal must be asserted low
during a bus cycle for the RTC portion of the DS1689/DS1693 to be
accessed. CS must be kept in the active state during RD and WR
timing. Bus cycles, which take place with ALE asserted but without
asserting, CS will latch addresses. However, no data transfer will
occur.
17 17 ALE
Address Strobe Input (Active High). A pulse on the address strobe
pin serves to demultiplex the bus. The falling edge of ALE causes
the RTC address to be latched within the DS1689/DS1693.
18 18 WR
Active-Low Write Data Strobe. The WR signal is an active low
signal. The WR signal defines the time period during which data is
written to the addressed register.
20 20 RD
Active-Low Read Data Strobe. RD identifies the time period when
the DS1689/DS1693 drives the bus with RTC read data. The RD
signal is an enable signal for the output buffers of the clock.
21 21 PSEL
+3V or +5V Power Select. When PSEL is logic 1, 5V operation is
selected. When PSEL is logic 0 or is floated, the device is in
autosense mode and determines the correct mode of operation based
on the voltage on VCCI.
22 22 IRQ
Active-Low Interrupt Request Output (Open Drain). The IRQ pin is
an active-low output of the DS1689/DS1693 that can be tied to the
interrupt input of a processor. The IRQ output remains low as long
as the status bit causing the interrupt is present and the
corresponding interrupt-enable bit is set. To clear the IRQ pin, the
application software must clear all enabled flag bits contributing to
IRQ’s active state. When no interrupt conditions are present, the IRQ
level is in the high impedance state. Multiple interrupting devices
can be connected to an IRQ bus. The IRQ pin is an open-drain
output and requires an external pullup resistor.
Battery Input for Any Standard 3V Lithium Cell or Other Energy
DS1689/DS1693
PIN
SO EDIP NAME FUNCTION 24 24 SQW
Square-Wave Output. The SQW pin can output a signal from one of
13 taps provided by the 15 internal divider stages of the real time
clock. The frequency of the SQW pin can be changed by
programming Register A as shown in Table 2. The SQW signal can
be turned on and off using the SQWE bit in Register B. A 32kHz
SQW signal is output when SQWE = 1, the Enable 32kHz (E32K)
bit in extended register 04BH is logic 1, and VCC is above VPF. A
32kHz square wave is also available when VCC is less than VPF if
E32K = 1, ABE = 1, and voltage is applied to VBAUX.
25 25 VCCO
External SRAM Power-Supply Output. This pin is internally
connected to VCCI when VCCI is within nominal limits. However,
during power fail, VCCO is internally connected to the VBAT or VBAUX
(whichever is larger). For 5V operation, switchover from VCCI to the
backup supply occurs when VCCI drops below the larger of VBAT and
VBAUX. For 3V operation, switchover from VCCI to the backup supply
occurs at VPF if VPF is less than VBAT and VBAUX. If VPF is greater
than VBAT and VBAUX, the switch from VCCI to the backup supply
occurs when VCCI drops below the larger of VBAT and VBAUX.
26 26 VCCI
+3V or +5V Main Supply. DC power is provided to the device on
these pins. 5V operation is selected when the PSEL pin is at logic 1.
If PSEL is floated or at logic 0, the device is in autosense mode and
determines the correct operating voltage based on the VCCI voltage
level.
27 27 CEO
Active-Low RAM Chip Enable Output. When power is valid, CEO
will equal CEI. When power is not valid, CEO will be driven high
regardless of CEI.
28 28 CEI Active-Low RAM Chip Enable Input. CEI should be driven low to
enable the external RAM. 2, 3,
19, 23 N.C. No Connection
DS1689/DS1693
DETAILED DESCRIPTION The DS1689/DS1693 are real-time clocks (RTCs) designed as successors to the industry standard
DS1285, DS1385, DS1485, and DS1585 PC real-time clocks. These devices provide the industry
standard DS1285 clock function with the new feature of either +3.0V or +5.0V operation and automatic
backup and write protection to an external SRAM. The DS1689 also incorporates a number of enhanced
features including a silicon serial number, power-on/off control circuitry, and 114 bytes of user NV
SRAM, power-on elapsed timer, and power-cycle counter.
Each DS1689/DS1693 is individually manufactured with a unique 64-bit serial number as well as an
additional 64-bit customer specific ROM or serial number. The serial number is programmed and tested
at Dallas to ensure that no two devices are alike. The serial number can be used to electronically identify
a system for purposes such as establishment of a network node address or for maintenance tracking.
Customers can reserve blocks of available numbers from Dallas Semiconductor.
The serialized RTCs also incorporate power control circuitry, which allows the system to be powered on
via an external stimulus, such as a keyboard or by a time and date (wake-up) alarm. The PWR output pin
can be triggered by one or either of these events, and can be used to turn on an external power supply.
The PWR pin is under software control, so that when a task is complete, the system power can then be
shut down.
The DS1689/DS1693 incorporate a power-on elapsed time counter, a power-on cycle counter, and a
battery powered continuous counter. These three counters provide valuable information for maintenance
and warranty requirements.
Automatic backup and write protection for an external SRAM is provided through the VCCO and CEO
pins. The lithium energy source used to permanently power the real time clock is also used to retain RAM
data in the absence of VCC power through the VCCO pin. The chip enable output to RAM (CEO) is
controlled during power transients to prevent data corruption.
The DS1689 is a clock/calendar chip with the features described above. An external crystal and battery
are the only components required to maintain time-of-day and memory status in the absence of power.
The DS1693 incorporates the DS1689 chip, a 32.768kHz crystal, and a lithium battery in a complete, self-
contained timekeeping module. The entire unit is fully tested at Dallas Semiconductor such that a
minimum of 10 years of timekeeping and data retention in the absence of VCC is guaranteed.
OPERATION The block diagram in Figure 1 shows the pin connections with the major internal functions of the
DS1689/DS1693. The following paragraphs describe the function of each pin.
DS1689/DS1693
Figure 1. DS1689/DS1693 Block Diagram DS1689/DS1693
POWER-DOWN/POWER-UP CONSIDERATIONS The real-time clock function will continue to operate and all of the RAM, time, calendar, and alarm
memory locations remain nonvolatile regardless of the level of the VCCI input. When VCCI is applied to
the DS1689/DS1693 and reaches a level of greater than VPF (power fail trip point), the device becomes
accessible after tREC, provided that the oscillator is running and the oscillator countdown chain is not in
reset (see Register A). This time period allows the system to stabilize after power is applied.
When PSEL is floating or logic 0, the DS1689 is in autosense mode and 3V or 5V operation is
determined based on the voltage on VCCI. Selection of 5V operation is automatically invoked when VCCI
rises above 4.5V for a minimum of tREC. However, 3V operation is automatically selected if VCCI does not
rise above the level of 4.25V. Selection of the power supply input levels requires 150ms of input stability
before operation can commence.
When 5V operation is selected, the device is fully accessible and data can be written and read only when
VCCI is greater than 4.5V. When VCCI is below 4.5V, read and writes are inhibited. However, the
timekeeping function continues unaffected by the lower input voltage. As VCC falls below the greater of
VBAT and VBAUX, the RAM and timekeeper are switched over to a lithium battery connected either to the
VBAT pin or VBAUX pin.
When 3V operation is selected and applied within normal limits, the device is fully accessible and data
can be written or read. When VCCI falls below VPF, access to the device is inhibited. If VPF is less than
VBAT and VBAUX, the power supply is switched from VCCI to the backup supply (the greater of VBAT and
VBAUX) when VCCI drops below VPF. If VPF is greater than VBAT and VBAUX, the power supply is switched
from VCCI to the backup supply when VCCI drops below the larger of VBAT and VBAUX.
When VCC falls below VPF, the chip is write-protected. With the possible exception of the KS, PWR, and
SQW pins, all inputs are ignored and all outputs are in a high impedance state.
RTC ADDRESS MAP The address map for the RTC registers of the DS1689/DS1693 is shown in Figure 2. The address map
consists of the 14-clock/calendar registers. Ten registers contain the time, calendar, and alarm data, and
four bytes are used for control and status. All registers can be directly written or read except for the
following:
1. Registers C and D are read-only.
2. Bit 7 of Register A is read-only.
3. The high order bit of the seconds byte is read-only.
DS1689/DS1693
Figure 2. DS1689 Real-Time Clock Address Map
TIME, CALENDAR, AND ALARM LOCATIONS The time and calendar information is obtained by reading the appropriate register bytes shown in Table 1.
The time, calendar, and alarm are set or initialized by writing the appropriate register bytes. The contents
of the time, calendar, and alarm registers can be either Binary or Binary-Coded Decimal (BCD) format.
Table 1 shows the binary and BCD formats of the twelve time, calendar, and alarm locations that reside in
both bank 0 and in bank 1, plus the two extended registers that reside in bank 1 only (bank 0 and bank 1
switching will be explained later in this text).
Before writing the internal time, calendar, and alarm registers, the SET bit in Register B should be written
to a logic 1 to prevent updates from occurring while access is being attempted. Also at this time, the data
format (binary or BCD) should be set via the data mode bit (DM) of Register B. All time, calendar, and
alarm registers must use the same data mode. The set bit in Register B should be cleared after the data
mode bit has been written to allow the real-time clock to update the time and calendar bytes.
Once initialized, the real-time clock makes all updates in the selected mode. The data mode cannot be
changed without reinitializing the 10 data bytes. The 24/12 bit cannot be changed without reinitializing
the hour locations. When the 12-hour format is selected, the high order bit of the hours byte represents
PM when it is a logic 1. The time, calendar, and alarm bytes are always accessible because they are
double-buffered. Once per second the 10 bytes are advanced by one second and checked for an alarm
condition. If a read of the time and calendar data occurs during an update, a problem exists where
seconds, minutes, hours, etc. may not correlate. The probability of reading incorrect time and calendar
data is low. Several methods of avoiding any possible incorrect time and calendar reads are covered later
in this text.
The four alarm bytes can be used in two ways. First, when the alarm time is written in the appropriate
hours, minutes, and seconds alarm locations, the alarm interrupt is initiated at the specified time each day
if the alarm enable bit is high. The second use condition is to insert a “don’t care” state in one or more of
the four alarm bytes. The “don’t care” code is any hexadecimal value from C0 to FF. The two most
DS1689/DS1693
minute with “don’t care” codes in the hours and minute alarm bytes. The “don’t care” codes in all three
alarm bytes create an interrupt every second. The three alarm bytes may be used in conjunction with the
date alarm as described in the Wakeup/Kickstart section. The century counter will be discussed later in
this text.
Table 1. Time, Calendar, and Alarm Data Modes
RANGE ADDRESS
LOCATION FUNCTION DECIMAL
RANGE BINARY DATA
MODE
BCD DATA
MODE 00H Seconds 0-59 00-3B 00-59
01H Seconds Alarm 0-59 00-3B 00-59
02H Minutes 0-59 00-3B 00-59
03H Minutes Alarm 0-59 00-3B 00-59
Hours 12-hr Mode 1-12 01-0C AM, 81-8C PM 01-12 AM, 81-92 PM 04H Hours 24-hr Mode 0-23 00-17 00-23
Hours Alarm 12-hr
Mode 1-12 01-0C AM, 81-8C PM 01-12 AM, 81-92 PM
05H Hours Alarm 24-hr
Mode 0-23 00-17 00-23
06H Day of Week
Sunday=1 1-7 01-07 01-07
07H Date of Month 1-31 01-1F 01-31
08H Month 1-12 01-0C 01-12
09H Year 0-99 00-63 00-99
BANK1, 48H Century 0-99 00-63 00-99
BANK 1, 49H Date Alarm 1-31 01-1F 01-31
CONTROL REGISTERS The four control registers; A, B, C, and D reside in both bank 0 and bank 1. These registers are accessible
at all times, even during the update cycle.
NONVOLATILE RAM—RTC The 114 general-purpose nonvolatile RAM bytes are not dedicated to any special function within the
DS1689/DS1693. They can be used by the application program as nonvolatile memory and are fully
available during the update cycle. This memory is directly accessible when bank 0 is selected.
INTERRUPT CONTROL The DS1689/DS1693 include six separate, fully automatic sources of interrupt for a processor:
1. Alarm interrupt
2. Periodic interrupt
3. Update-ended interrupt
4. Wake-up interrupt
5. Kickstart interrupt
6. RAM clear interrupt
The conditions, which generate each of these independent interrupt conditions, are described in greater
DS1689/DS1693
The application software can select which interrupts, if any, are to be used. A total of 6 bits, including 3
bits in Register B and 3 bits in Extended Register B, enable the interrupts. The extended register locations
are described later. Writing logic 1 to an interrupt enable bit permits that interrupt to be initiated when the
event occurs. A logic 0 in the interrupt enable bit prohibits the IRQ pin from being asserted from that
interrupt condition. If an interrupt flag is already set when an interrupt is enabled, IRQ is immediately set
at an active level, even though the event initiating the interrupt condition may have occurred much earlier.
As a result, there are cases where the software should clear these earlier generated interrupts before first
enabling new interrupts.
When an interrupt event occurs, the relating flag bit is set to a logic 1 in Register C or in Extended
Register A. These flag bits are set regardless of the setting of the corresponding enable bit located either
in Register B or in Extended Register B. The flag bits can be used in a polling mode without enabling the
corresponding enable bits.
However, care should be taken when using the flag bits of Register C as they are automatically cleared to
0 immediately after they are read. Double latching is implemented on these bits so that bits that are set
remain stable throughout the read cycle. All bits which were set are cleared when read and new interrupts
which are pending during the read cycle are held until after the cycle is completed. One, 2, or 3 bits can
be set when reading Register C. Each utilized flag bit should be examined when read to ensure that no
interrupts are lost.
The flag bits in Extended Register A are not automatically cleared following a read. Instead, each flag bit
can be cleared to 0 only by writing 0 to that bit.
When using the flag bits with fully enabled interrupts, the IRQ line is driven low when an interrupt flag
bit is set and its corresponding enable bit is also set. IRQ is held low as long as at least one of the six
possible interrupt sources has it s flag and enable bits both set. The IRQF bit in Register C is 1 whenever
the IRQ pin is being driven low as a result of one of the six possible active sources. Therefore,
determination that the DS1689/DS1693 initiated an interrupt is accomplished by reading Register C and
finding IRQF = 1. IRQF remains set until all enabled interrupt flag bits are cleared to 0.
SQUARE-WAVE OUTPUT SELECTION The SQW pin can be programmed to output a variety of frequencies divided down from the 32.768kHz
crystal tied to X1 and X2. The square-wave output is enabled and disabled via the SQWE bit in Register
B. If the square wave is enabled (SQWE = 1), the output frequency is determined by the settings of the
E32K bit in Extended Register B and by the RS3–RS0 bits in Register A. If the E32K = 1, then a
32.768kHz square wave is output on the SQW pin regardless of the settings of RS3–RS0.
If E32K = 0, then the square-wave output frequency is determined by the RS3–RS0 bits. These bits
control a 1-of-15 decoder, which selects one of 13 taps that divide the 32.768kHz frequency. The RS3–
RS0 bits establish the SQW output frequency as shown in Table 2. In addition, RS3–RS0 bits control the
periodic interrupt selection as described below.
If SQWE1, E32K = 1, and the auxiliary battery enable bit (ABE, bank 1; register 04BH) is enabled, and
voltage is applied to VBAUX, then the 32kHz square-wave output signal is output on the SQW pin in the
absence of VCC. This facility is provided to clock external power management circuitry. If any of the
above requirements are not met, no square-wave output signal is generated on the SQW pin in the
DS1689/DS1693
A pattern of 01X in the DV2, DV1, and DV0, bits respectively, turns the oscillator on and enables the
countdown chain. Note that this is different than the DS1287, which required a pattern of 010 in these
bits. DV0 is now a “don’t care” because it is used for selection between register banks 0 and 1. A pattern
of 11X turns the oscillator on, but the oscillator’s countdown chain is held in reset, as it was in the
DS1287. Any other bit combination for DV2 and DV1 keeps the oscillator off.
PERIODIC INTERRUPT SELECTION The periodic interrupt causes the IRQ pin to go to an active state from once every 500ms to once every
122µs. This function is separate from the alarm interrupt, which can be output from once per second to
once per day. The periodic interrupt rate is selected using the same RS3–RS0 bits in Register A, which
select the square-wave frequency (Table 2). Changing the bits affects both the square-wave frequency and
the periodic interrupt output. However, each function has a separate enable bit in Register B. The SQWE
bit controls the square-wave output. Similarly, the periodic interrupt is enabled by the PIE bit in Register
B. The periodic interrupt can be used with software counters to measure inputs, create output intervals, or
await the next needed software function.
UPDATE CYCLE The serialized RTC executes an update cycle once per second regardless of the SET bit in Register B.
When the SET bit in Register B is set to 1, the user copy of the double-buffered time, calendar, alarm and
elapsed time byte is frozen and does not update as the time increments. However, the time countdown
chain continues to update the internal copy of the buffer. This feature allows the time to maintain
accuracy independent of reading or writing the time, calendar, and alarm buffers and also guarantees that
time and calendar information is consistent. The update cycle also compares each alarm byte with the
corresponding time byte and issues an alarm if a match or if a “don’t care” code is present in all three
positions.
There are three methods that can handle access of the real-time clock that avoid any possibility of
accessing inconsistent time and calendar data. The first method uses the update-ended interrupt. If
enabled, an interrupt occurs after every up date cycle that indicates that over 999ms are available to read
valid time and date information. If this interrupt is used, the IRQF bit in Register C should be cleared
before leaving the interrupt routine.
A second method uses the update-in-progress bit (UIP) in Register A to determine if the update cycle is in
progress. The UIP bit will pulse once per second. After the UIP bit goes high, the update transfer occurs
244µs later. If a low is read on the UIP bit, the user has at least 244µs before the time/calendar data will
be changed. Therefore, the user should avoid interrupt service routines that would cause the time needed
to read valid time/calendar data to exceed 244µs.
DS1689/DS1693
Table 2. Periodic Interrupt Rate and Square-Wave Output Frequency
EXT. REG. B SELECT BITS REGISTER A
E32K RS3 RS2 RS1 RS0
tPI PERIODIC
INTERRUPT RATE
SQW OUTPUT
FREQUENCY 0 0 0 0 None None 0 0 0 1 3.90625ms 256Hz 0 0 1 0 7.8125ms 128Hz 0 0 1 1 122.070µs 8.192kHz 0 1 0 0 244.141µs 4.096kHz 0 1 0 1 488.281µs 2.048kHz 0 1 1 0 976.5625µs 1.024kHz 0 1 1 1 1.953125ms 512Hz 1 0 0 0 3.90625ms 256Hz 1 0 0 1 7.8125ms 128Hz 1 0 1 0 15.625ms 64Hz 1 0 1 1 31.25ms 32Hz 1 1 0 0 62.5ms 16Hz 1 1 0 1 125ms 8Hz 1 1 1 0 250ms 4Hz 1 1 1 1 500ms 2Hz X X X X (See Note) 32.768kHz
Note: RS3–RS0 determine periodic interrupt rates as listed for E32K = 0. The third method uses a periodic interrupt to determine if an update cycle is in progress. The UIP bit in
Register A is set high between the setting of the PF bit in Register C (see Figure 3). Periodic interrupts
that occur at a rate of greater than tBUC allow valid time and date information to be reached at each
occurrence of the periodic interrupt. The reads should be complete within (tPI / 2 + tBUC) to ensure that
data is not read during the update cycle.
Figure 3. Update-Ended and Periodic Interrupt Relationship DS1689/DS1693
REGISTER A
MSB LSB
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 UIP DV2 DV1 DV0 RS3 RS2 RS1 RS0
Bit 7: UIP (Update In Progress). This bit is a status flag that can be monitored. When the UIP bit is 1, the update transfer will soon occur. When UIP is 0, the update transfer will not occur for at least 244ms.
The time, calendar, and alarm information in RAM is fully available for access when the UIP bit is 0. The
UIP bit is read-only. Writing the SET bit in Register B to 1 inhibits any update transfer and clears the UIP
status bit.
Bits 6, 5, 4: DV0, DV1, DV2. These bits are defined as follows: DV2 = Countdown Chain
1 - resets countdown chain only if DV1 = 1
0 - countdown chain enabled
DV1 = Oscillator Enable
0 - oscillator off
1 - oscillator on
DV0 = Bank Select
0 - original bank
1 - extended registers
A pattern of 01X is the only combination of bits that turn the oscillator on and allow the RTC to keep
time. A pattern of 11X enables the oscillator but holds the countdown chain in reset. The next update
occurs at 500ms after a pattern of 01X is written to DV2, DV1, and DV0.
Bits 3 to 0: RS3 to RS0 (Rate Selection Bits). These four rate-selection bits select one of the 13 taps on the 15-stage divider or disable the divider output. The tap selected can be used to generate an output
square wave (SQW pin) and/or a periodic interrupt. The user can do one of the following:
Enable the interrupt with the PIE bit;
Enable the SQW output pin with the SQWE bit;
Enable both at the same time and the same rate; or
Enable neither.
Table 2 lists the periodic interrupt rates and the square-wave frequencies that can be chosen with the RS
bits.
DS1689/DS1693
REGISTER B
MSB LSB
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 SET PIE AIE UIE SQWE DM 24/12 DSE
Bit 7: SET. When the SET bit is 0, the update transfer functions normally by advancing the counts once per second. When the SET bit is written to 1, any update transfer is inhibited and the program can
initialize the time and calendar bytes without an update occurring in the midst of initializing. Read cycles
can be executed in a similar manner. SET is a read/write bit that is not modified by internal functions of
the DS1689/DS1693.
Bit 6: PIE (Periodic Interrupt Enable). This bit is a read/write bit that allows the periodic interrupt flag (PF) bit in Register C to drive the IRQ pin low. When the PIE bit is set to 1, periodic interrupts are
generated by driving the IRQ pin low at a rate specified by the RS3–RS0 bits of Register A. A 0 in the
PIE bit blocks the IRQ output from being driven by a periodic interrupt, but the periodic flag (PF) bit is
still set at the periodic rate. PIE is not modified by any internal DS1689/DS1693 functions.
Bit 5: AIE (Alarm Interrupt Enable). This bit is a read/write bit which, when set to 1, permits the alarm flag (AF) bit in Register C to assert IRQ. An alarm interrupt occurs for each second that the three time
bytes equal the three alarm bytes, including a don’t care alarm code of binary 11XXXXXX. When the
AIE bit is set to 0, the AF bit does not initiate the IRQ signal. The internal functions of the
DS1689/DS1693 do not affect the AIE bit.
Bit 4: UIE (Update-Ended Interrupt Enable). This bit is a read/write that enables the update-end flag (UF) bit in Register C to assert IRQ. The SET bit going high clears the UIE bit.
Bit 3: SQWE (Square-Wave Enable). When this bit is set to 1, a square-wave signal at the frequency set by the rate-selection bits RS3–RS0 and the E32K bit is driven out on the SQW pin. When the SQWE
bit is set to 0, the SQW pin is held low. SQWE is a read/write bit.
Bit 2: DM (Data Mode). This bit indicates whether time and calendar information is in binary or BCD format. The DM bit is set by the program to the appropriate format and can be read as required. This bit is
not modified by internal functions. A 1 in DM signifies binary data while a 0 in DM specifies Binary
Coded Decimal (BCD) data.
Bit 1: 24/12 (24/12 Control Bit). This bit establishes the format of the hours byte. A 1 indicates the 24-hour mode and a 0 indicates the 12-hour mode. This bit is read/write.
Bit 0: DSE (Daylight Saving Enable). This bit is a read/write bit which enables two special updates when DSE is set to 1. On the first Sunday in April the time increments from 1:59:59 am to 3:00:00 AM.
On the last Sunday in October when the time first reaches 1:59:59 AM it changes to 1:00:00 AM. These
special updates do not occur when the DSE bit is 0. This bit is not affected by internal functions.
DS1689/DS1693
REGISTER C
MSB LSB
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 IRQF PF AF UF 0 0 0 0
Bit 7: IRQF (Interrupt Request Flag). This bit is set to 1 when one or more of the following are true: PF = PIE = 1 WF = WIE = 1
AF = AIE = 1 KF = KSE = 1
UF = UIE = 1 RF = RIE = 1
i.e., IRQF = (PF • PIE) + (AF • AIE) + (UF • UIE) + (WF • WIE) + (KF • KSE) + (RF • RIE)
Any time the IRQF bit is 1, the IRQ pin is driven low. Flag bits PF, AF, and UF are cleared after Register
C is read by the program.
Bit 6: PF (Periodic Interrupt Flag). This bit is a read-only bit that is set to a 1 when an edge is detected on the selected tap of the divider chain. The RS3–RS0 bits establish the periodic rate. PF is set to 1
independent of the state of the PIE bit. When both PF and PIE are 1s, the IRQ signal is active and will set
the IRQF bit. The PF bit is cleared by a software read of Register C.
Bit 5: AF (Alarm Interrupt Flag). A 1 in the AF bit indicates that the current time has matched the
alarm time. If the AIE bit is also 1, the IRQ pin goes low and a 1 appears in the IRQF bit. A read of
Register C clears AF.
Bit 4: UF (Update-Ended Interrupt Flag). This bit is set after each update cycle. When the UIE bit is set to 1, the 1 in UF causes the IRQF bit to be 1, which asserts the IRQ pin. UF is cleared by reading
Register C.
Bits 3 to 0: Unused. These bits always read 0 and cannot be written.
REGISTER D
MSB LSB
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 VRT 0 0 0 0 0 0 0
Bit 7: VRT (Valid RAM and Time). This bit indicates the condition of the battery connected to the VBAT pin or the battery connected to VBAUX, whichever is at a higher voltage. This bit is not writable and
should always be a 1 when read. If a 0 is ever present, an exhausted lithium energy source is indicated
and both the contents of the RTC data and RAM data are questionable.
Bits 6 to 0: Unused. These bits cannot be written and always read 0 when read. DS1689/DS1693
EXTENDED FUNCTIONS The extended functions provided by the DS1689/DS1693 that are new to the RAMified RTC family are
accessed via a software-controlled bank-switching scheme, as illustrated in Figure 4. In bank 0, the
clock/calendar registers and 50 bytes of user RAM are in the same locations as for the DS1287. As a
result, existing routines implemented within BIOS, DOS, or application software packages can gain
access to the DS1689/DS1693 clock registers with no changes. Also in bank 0, an extra 64 bytes of RAM
are provided at addresses just above the original locations for a total of 114 directly addressable bytes of
user RAM.
When bank 1 is selected, the clock/calendar registers and the original 50 bytes of user RAM still appear
as bank 0. However, the Dallas registers which provide control and status for the extended functions will
be accessed in place of the additional 64 bytes of user RAM. The major extended functions controlled by
the Dallas registers are listed below:
1. Silicon Revision byte
2. Serial Number
3. 8-Byte Customer Specific ROM or Serial Number
4. Century counter
5. Auxiliary Battery Control/Status
6. Wake-Up
7. Kickstart
8. RAM Clear Control/Status
9. VCC Powered Elapsed Time Counter
10. VBAT Powered Elapsed Time Counter
11. Power-on Cycle Counter
The bank selection is controlled by the state of the DV0 bit in Register A. To access bank 0 the DV0 bit
should be written to 0. To access bank 1, DV0 should be written to 1. Register locations designated as
reserved in the bank 1 map are reserved for future use by Dallas Semiconductor. Bits in these locations
cannot be written and return a 0 if read.
DS1689/DS1693
Figure 4. DS1689/DS1693 Extended Register Bank Definition DS1689/DS1693
SILICON SERIAL NUMBER/CUSTOMER SPECIFIC ROM A total of 128 bits are available for use as serial number/ROM. These bits can be used as a 128-bit serial
number or as a unique 64-bit serial number and 64-bit customer specific serial number or ROM. The
unique 64-bit serial number is located in bank 1 registers 40H–47H. This serial number is divided into
three parts. The first byte in register 40H contains a model number to identify the device type and
revision of the DS1689/DS1693. Registers 41H–46H contain a unique binary number. Register 47H
contains a CRC byte used to validate the data in registers 40H–46H. The method used to create the CRC
byte is proprietary to Dallas Semiconductor, but can be made available if required. Typical applications
should consider this byte simply as part of the overall unique serial number. All 8 bytes of the serial
number are read-only registers.
The DS1689/DS1693 are manufactured such that no two devices contain an identical number in locations
41H–47H. Customers can reserve blocks of numbers for these locations. Contact Dallas Semiconductor
for special ordering information for DS1689/DS1693 with reserved blocks of serial numbers.
As already mentioned, another 64 bits are available for use as an additional serial number or customer
specific ROM. These 64 bits are located in bank 1 registers 60H–67H.
CENTURY COUNTER A register has been added in bank 1, location 48H, to keep track of centuries. The value is read in either
binary or BCD according to the setting of the DM bit.
AUXILIARY BATTERY The VBAUX input is provided to supply power from an auxiliary battery for the DS1689/DS1693 kickstart,
wake-up, and SQW output features in the absence of VCC. This power source must be available in order to
use these auxiliary features when no VCC is applied to the device.
The auxiliary battery enable (ABE; bank 1, register 04BH) bit in extended Control Register B is used to
turn on and off the auxiliary battery for the above functions in the absence of VCC. When set to a 1, VBAUX
battery power is enabled, and when cleared to 0, VBAUX battery power is disabled to these functions.
In the DS1689/DS1693, this auxiliary battery can be used as the primary backup power source for
maintaining the clock/calendar, user RAM, and extended external RAM functions. This occurs if the
VBAT pin is at a lower voltage than VBAUX. If the DS1689 is to be backed up using a single battery with
the auxiliary features enabled, then VBAUX should be used and connected to VBAT. If VBAUX is not to be
used, it should be grounded and ABE should be cleared to 0.
WAKE-UP/KICKSTART The DS1689/DS1693 incorporate a wake-up feature, which can power the system on at a predetermined
date through activation of the PWR output pin. In addition, the kickstart feature can allow the system to
be powered-up in response to a low-going transition on the KS pin, without operating voltage applied to
the VCC pin. As a result, system power can be applied upon such events as a key closure, or modem ring
detect signal. To use either the wake-up or the kickstart features, the DS1689/DS1693 must have an
auxiliary battery connected to the VBAUX pin, and the oscillator must be running and the countdown chain
must not be in reset (Register A DV2, DV1, DV0 = 01X). If DV2, DV1, and DV0 are not in this required
state, the PWR pin is not driven low in response to a kickstart or wakeup condition, while in battery-
