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DS1689/DS1693
3-Volt/5-Volt Serialized Real Time Clock
with NV RAM Control
www.dalsemi.com
FEATURES
Incorporates industry standard DS1287 PC clock
plus enhanced features:
§
+3- or +5-volt 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
6 pF or 12.5 pF crystal
§
114 bytes user NV RAM
§
Auxiliary battery input
§
RAM clear input
§
Century register
§
32 kHz output for power management
§
32-bit V
CC
powered elapsed time counter
§
32-bit V
BAT
powered elapsed time counter
§
16-bit power cycle counter
§
Compatible with existing BIOS for original
DS1287 functions
§
Available as chip (DS1689) or standalone
module with embedded battery and crystal
(DS1693)
§
Chips are available in industrial temperature
version
§
Timekeeping algorithm includes leap year
compensation valid up to 2100
PIN ASSIGNMENT
V
BAUX
X1
X2
RCLR
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
PWR
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
V
BAUX
CEI
X1
CEO
X2
V
CCI
V
CCO
RCLR
AD0
SQW
V
BAT
AD1
AD2
IRQ
PSEL AD3
AD4
RD
AD5
GND
AD6
WR
AD7
ALE
PWR
CS
GND
KS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
CEI
CEO
V
CCI
V
CCO
SQW
V
BAT
IRQ
PSEL
RD
GND
WR
ALE
CS
KS
DS1689 28-Pin DIP
(600-mil)
V
BAUX
NC
NC
RCLR
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
PWR
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
DS1689S 28-Pin SOIC
(330-mil)
28
27
26
25
24
23
22
21
20
19
18
17
16
15
CEI
CEO
V
CCI
V
CCO
SQW
NC
IRQ
PSEL
RD
GND
WR
ALE
CS
KS
DS1693 28-Pin ENCAPSULATED
PACKAGE (740-mil)
PIN DESCRIPTION
X1
X2
RCLR
ORDERING INFORMATION
PART #
DS1689
DS1689S
DS1693
DESCRIPTION
RTC Chip, 28-pin DIP
RTC Chip, 28-pin SOIC
RTC Module; 28-pin DIP
AD0-AD7
PWR
KS
CS
ALE
WR
RD
V
CCO
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- Crystal Input
- Crystal Output
- RAM Clear Input
- Mux’ed Address/Data Bus
- Power-on Interrupt Output
(open drain)
- Kickstart Input
- RTC Chip Select Input
- RTC Address Strobe
- RTC Write Data Strobe
- RTC Read Data Strobe
- RAM Power Supply Output
080299
DS1689/DS1693
IRQ
SQW
V
CCI
GND
- Interrupt Request Output
(open drain)
- Square Wave Output
- +3- or +5-Volt Main Supply
- Ground
V
BAT
V
BAUX
PSEL
CEI
CEO
- Battery + Supply
- Auxiliary Battery Supply
- +3- or +5-Volt Power Select
- RAM Chip Enable In
- RAM Chip Enable Out
DESCRIPTION
The DS1689/DS1693 is a real time clock (RTC) designed as a successor to the industry standard DS1285,
DS1385, DS1485, and DS1585 PC real time clocks. This device provides the industry standard DS1285
clock function with the new feature of either +3.0- or +5.0-volt 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, 114 bytes of user NVSRAM, 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 insure 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. Blocks
of available numbers from Dallas Semiconductor can be reserved by the customer.
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 incorporates 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 V
CCO
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 V
CC
power through the V
CCO
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 32.768 kHz 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 V
CC
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.
SIGNAL DESCRIPTIONS
GND, V
CCI
- DC power is provided to the device on these pins. V
CCI
is the +3-volt or +5-volt input. Five-
volt operation is selected when the PSEL pin is at a logic 1. If PSEL is floated or at a logic 0, the device
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DS1689/DS1693
will be in auto-sense mode and will determine the correct operating voltage based on the V
CCI
voltage
level.
PSEL (Power Select Input)
- This pin selects whether 3-volt operation or 5-volt operation will be used.
When PSEL is a logic 1, 5-volt operation is selected. When PSEL is a logic 0 or is floated, the device will
be in auto-sense mode and will determine the correct mode of operation based on the voltage on V
CCI
.
V
CCO
(External SRAM Power Supply Output)
- This pin will be internally connected to V
CCI
when
V
CCI
is within nominal limits. However, during power fail, V
CCO
will be internally connected to the V
BAT
or V
BAUX
(whichever is larger). For 5-volt operation, switch over from V
CCI
to the backup supply occurs
when V
CCI
drops below the larger of V
BAT
and V
BAUX
. For 3-volt operation, switch over from V
CCI
to the
backup supply occurs at V
PF
if V
PF
is less than V
BAT
and V
BAUX
. If V
PF
is greater than V
BAT
and V
BAUX
,
the switch from V
CCI
to the backup supply occurs when V
CCI
drops below the larger of V
BAT
and V
BAUX
.
DS1689/DS1693 BLOCK DIAGRAM
Figure 1
3 of 32
DS1689/DS1693
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 32 kHz SQW signal is output when SQWE=1, the Enable 32 kHz (E32K) bit in
extended register 04BH is a logic 1, and V
CC
is above V
PF
. A 32 kHz square wave is also available when
V
CC
is less than V
PF
if E32K=1, ABE=1, and voltage is applied to V
BAUX
.
AD0-AD7 (Multiplexed Bidirectional 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.
ALE (RTC 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.
(RTC Read Input; active low)
-
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.
RD
WR
(RTC Write Input; active low)
- The
WR
signal is an active low signal. The
WR
signal defines
the time period during which data is written to the addressed register.
CS
(RTC Chip Select Input; active low)
- The Chip Select 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.
IRQ
(Interrupt Request Output; open drain, active low)
- 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 pull-up resistor.
CEI
(RAM Chip Enable Input; active low)
-
CEI
should be driven low to enable the external RAM.
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