DS1305 Serial Alarm Real

DS1305 Serial Alarm Real
DS1305
Serial Alarm Real-Time Clock
FEATURES
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PIN CONFIGURATIONS
Real-Time Clock (RTC) Counts Seconds,
Minutes, Hours, Date of the Month, Month,
Day of the Week, and Year with Leap-Year
Compensation Valid Up to 2100
96-Byte, Battery-Backed NV RAM for Data
Storage
Two Time-Of-Day Alarms, Programmable
on Combination of Seconds, Minutes, Hours,
and Day of the Week
Supports Motorola SPI™ (Serial Peripheral
Interface) Modes 1 and 3 or Standard 3-Wire
Interface
Burst Mode for Reading/Writing Successive
Addresses in Clock/RAM
Dual-Power Supply Pins for Primary and
Backup Power Supplies
Optional Trickle Charge Output to Backup
Supply
2.0V to 5.5V Operation
Optional Industrial Temperature Range:
-40°C to +85°C
Available in Space-Efficient, 20-Pin TSSOP
Package
Underwriters Laboratory (UL) Recognized
TOP VIEW
VCC2
1
20
VCC1
VBAT
2
19
N.C.
X1
3
18
PF
VCCIF
DS1305
N.C.
4
17
X2
5
16
SD0
N.C.
6
15
SDI
INT0
7
14
SCLK
N.C.
8
13
N.C.
INT1
9
12
CE
GND
10
11
SERMODE
TSSOP (4.4mm)
VCC2
1
16
VCC1
VBAT
2
15
PF
14
VCCIF
13
SDO
X1
3
X2
4
DS1305
N.C.
5
12
SDI
INT0
6
11
SCLK
INT1
7
10
CE
GND
8
9
SERMODE
DIP (300 mils)
TYPICAL OPERATING CIRCUIT
SPI is a trademark of Motorola, Inc.
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REV: 070705
DS1305
ORDERING INFORMATION
PART
TEMP RANGE
PIN-PACKAGE
DS1305
DS1305E+
DS1305EN+
DS1305EN+T&R
DS1305E+T&R
DS1305E
DS1305EN
DS1305EN/T&R
DS1305E/T&R
DS1305N
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
16 DIP (300 mils)
20 TSSOP (173 mils)
20 TSSOP (173 mils)
20 TSSOP (173), Tape/Reel
20 TSSOP (173 mils), Tape/Reel
20 TSSOP (173)
20 TSSOP (173 mils)
20 TSSOP (173 mils), Tape/Reel
20 TSSOP (173 mils), Tape/Reel
16 DIP (300 mils)
TOP MARK*
DS1305
DS1305
DS1305N
DS1305
DS1305
DS1305
DS1305
DS1305
DS1305
DS1305N
+ Denotes a lead-free/RoHS-compliant device.
* An “N” on the top mark denotes an industrial device.
DESCRIPTION
The DS1305 serial alarm real-time clock provides a full binary coded decimal (BCD) clock calendar that
is accessed by a simple serial interface. The clock/calendar provides seconds, minutes, hours, day, date,
month, and year information. The end of the month date is automatically adjusted for months with fewer
than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour
format with AM/PM indicator. In addition, 96 bytes of NV RAM are provided for data storage. The
DS1305 will maintain the time and date, provided the oscillator is enabled, as long as at least one supply
is at a valid level.
An interface logic power-supply input pin (VCCIF) allows the DS1305 to drive SDO and PF pins to a level
that is compatible with the interface logic. This allows an easy interface to 3V logic in mixed supply
systems.
The DS1305 offers dual-power supplies as well as a battery input pin. The dual power supplies support a
programmable trickle charge circuit that allows a rechargeable energy source (such as a super cap or
rechargeable battery) to be used for a backup supply. The VBAT pin allows the device to be backed up by
a non-rechargeable battery. The DS1305 is fully operational from 2.0V to 5.5V.
Two programmable time-of-day alarms are provided by the DS1305. Each alarm can generate an
interrupt on a programmable combination of seconds, minutes, hours, and day. “Don’t care” states can be
inserted into one or more fields if it is desired for them to be ignored for the alarm condition. The time-ofday alarms can be programmed to assert two different interrupt outputs or to assert one common interrupt
output. Both interrupt outputs operate when the device is powered by VCC1, VCC2, or VBAT.
The DS1305 supports a direct interface to SPI serial data ports or standard 3-wire interface. A
straightforward address and data format is implemented in which data transfers can occur 1 byte at a time
or in multiple-byte-burst mode.
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DS1305
PIN DESCRIPTION
PIN
DIP
TSSOP
NAME
1
1
VCC2
2
2
VBAT
3
3
X1
4
5
X2
5
4, 6, 8,
13, 19
N.C.
6
7
INT0
7
9
INT1
8
10
GND
9
11
SERMODE
10
12
CE
11
14
SCLK
FUNCTION
Backup Power Supply. This is the secondary power supply pin. In systems
using the trickle charger, the rechargeable energy source is connected to this
pin.
Battery Input for Standard +3V Lithium Cell or Other Energy Source. If not
used, VBAT must be connect to ground. Diodes must not be placed in series
between VBAT and the battery, or improper operation will result. UL
recognized to ensure against reverse charging current when used in
conjunction with a lithium battery. See “Conditions of Acceptability” at
www.maxim-ic.com/TechSupport/QA/ntrl.htm.
Connections for Standard 32.768kHz Quartz Crystal. The internal oscillator is
designed for operation with a crystal having a specified load capacitance of
6pF. For more information on crystal selection and crystal layout
considerations, refer to Application Note 58: Crystal Considerations with
Dallas Real-Time Clocks. The DS1305 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.
No Connection
Active-Low Interrupt 0 Output. The INT0 pin is an active low output of the
DS1305 that can be used as an interrupt input to a processor. The INT0 pin
can be programmed to be asserted by only Alarm 0 or can be programmed to
be asserted by either Alarm 0 or Alarm 1. The INT0 pin remains low as long
as the status bit causing the interrupt is present and the corresponding interrupt
enable bit is set. The INT0 pin operates when the DS1305 is powered by VCC1,
VCC2, or VBAT. The INT0 pin is an open-drain output and requires an external
pullup resistor.
Active-Low Interrupt 1 Output. The INT1 pin is an active-low output of the
DS1305 that can be used as an interrupt input to a processor. The INT1 pin
can be programmed to be asserted by Alarm 1 only. The INT1 pin remains
low as long as the status bit causing the interrupt is present and the
corresponding interrupt enable bit is set. The INT1 pin operates when the
DS1305 is powered by VCC1, VCC2, or VBAT. The INT1 pin is an open-drain
output and requires an external pullup resistor. Both INT0 and INT1 are opendrain outputs. The two interrupts and the internal clock continue to run
regardless of the level of VCC (as long as a power source is present).
Ground
Serial Interface Mode. The SERMODE pin offers the flexibility to choose
between two serial interface modes. When connected to GND, standard 3-wire
communication is selected. When connected to VCC, SPI communication is
selected.
Chip Enable. The chip-enable signal must be asserted high during a read or a
write for both 3-wire and SPI communication. This pin has an internal 55kW
pulldown resistor (typical).
Serial Clock Input. SCLK is used to synchronize data movement on the serial
interface for either the SPI or 3-wire interface.
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DS1305
PIN DESCRIPTIONS (continued)
PIN
DIP
TSSOP
NAME
12
15
SDI
13
16
SDO
14
17
VCCIF
15
18
PF
16
20
VCC1
FUNCTION
Serial Data Input. When SPI communication is selected, the SDI pin is the
serial data input for the SPI bus. When 3-wire communication is selected, this
pin must be tied to the SDO pin (the SDI and SDO pins function as a single I/O
pin when tied together).
Serial Data Output. When SPI communication is selected, the SDO pin is the
serial data output for the SPI bus. When 3-wire communication is selected, this
pin must be tied to the SDI pin (the SDI and SDO pins function as a single I/O
pin when tied together).
Interface Logic Power-Supply Input. The VCCIF pin allows the DS1305 to drive
SDO and PF output pins to a level that is compatible with the interface logic,
thus allowing an easy interface to 3V logic in mixed supply systems. This pin is
physically connected to the source connection of the p-channel transistors in
the output buffers of the SDO and PF pins.
Active-Low Power-Fail Output. The PF pin is used to indicate loss of the
primary power supply (VCC1). When VCC1 is less than VCC2 or is less than VBAT,
the PF pin is driven low.
Primary Power Supply. DC power is provided to the device on this pin.
OPERATION
The block diagram in Figure 1 shows the main elements of the serial alarm RTC. The following
paragraphs describe the function of each pin.
Figure 1. BLOCK DIAGRAM
OSCILLATOR AND
COUNTDOWN CHAIN
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1Hz
DS1305
RECOMMENDED LAYOUT FOR CRYSTAL
Local ground plane (Layer 2)
X1
crystal
X2
GND
CLOCK ACCURACY
The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match
between the capacitive load of the oscillator circuit and the capacitive load for which the crystal was
trimmed. Additional error is added by crystal frequency drift caused by temperature shifts. External
circuit noise coupled into the oscillator circuit can result in the clock running fast. Refer to Application
Note 58, “Crystal Considerations with Dallas Real-Time Clocks” for detailed information.
CLOCK, CALENDAR, AND ALARM
The time and calendar information is obtained by reading the appropriate register bytes. The RTC
registers and user RAM are illustrated in Figure 2. The time, calendar, and alarm are set or initialized by
writing the appropriate register bytes. Note that some bits are set to 0. These bits always read 0 regardless
of how they are written. Also note that registers 12h to 1Fh (read) and registers 92h to 9Fh are reserved.
These registers always read 0 regardless of how they are written. The contents of the time, calendar, and
alarm registers are in the BCD format. The day register increments at midnight. Values that correspond to
the day of week are user-defined but must be sequential (e.g., if 1 equals Sunday, 2 equals Monday and so
on). Illogical time and date entries result in undefined operation.
Except where otherwise noted, the initial power on state of all registers is not defined. Therefore, it is
important to enable the oscillator (EOSC = 0) and disable write protect (WP = 0) during initial
configuration.
WRITING TO THE CLOCK REGISTERS
The internal time and date registers continue to increment during write operations. However, the
countdown chain is reset when the seconds register is written. Writing the time and date registers within
one second after writing the seconds register ensures consistent data.
Terminating a write before the last bit is sent aborts the write for that byte.
READING FROM THE CLOCK REGISTERS
Buffers are used to copy the time and date register at the beginning of a read. When reading in burst
mode, the user copy is static while the internal registers continue to increment.
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DS1305
Figure 2. RTC REGISTERS AND ADDRESS MAP
HEX ADDRESS
READ
WRITE
00H
80H
01H
81H
Bit7
0
0
02H
82H
0
03H
04H
05H
06H
83H
84H
85H
86H
0
0
0
—
—
07H
08H
87H
88H
M
M
09H
89H
M
0AH
8AH
M
—
—
0BH
0CH
8BH
8CH
M
M
0DH
8DH
M
0EH
0FH
10H
11H
12–1FH
20–7FH
8EH
8FH
90H
91H
92–9FH
A0–FFH
M
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
10 Seconds
Seconds
10 Minutes
Minutes
P
12
10 Hour
Hours
A
24
10
0
0
0
Day
0
10 Date
Date
0
10 Month
Month
10 Year
Year
Alarm 0
10 Seconds Alarm
Seconds Alarm
10 Minutes Alarm
Minutes Alarm
P
12
10 Hour
Hour Alarm
A
24
10
0
0
0
Day Alarm
Alarm 1
10 Seconds Alarm
Seconds Alarm
10 Minutes Alarm
Minutes Alarm
P
12
10 Hour
Hour Alarm
A
24
10
0
0
0
Day Alarm
Control Register
Status Register
Trickle Charger Register
Reserved
96 Bytes User RAM
Bit0
RANGE
00–59
00–59
01–12 + P/A
00–23
1–7
1–31
01–12
00–99
—
00–59
00–59
01–12 + P/A
00–23
01–07
—
00–59
00–59
01–12 + P/A
00–23
01–07
—
—
—
—
00–FF
Note: Range for alarm registers does not include mask’m’ bits.
The DS1305 can be run in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the
12- or 24-hour mode select bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is the
AM/PM bit with logic high being PM. In the 24-hour mode, bit 5 is the second 10-hour bit (20 to 23
hours).
The DS1305 contains two time-of-day alarms. Time-of-day Alarm 0 can be set by writing to registers 87h
to 8Ah. Time-of-day Alarm 1 can be set by writing to registers 8Bh to 8Eh. The alarms can be
programmed (by the INTCN bit of the control register) to operate in two different modes; each alarm can
drive its own separate interrupt output or both alarms can drive a common interrupt output. Bit 7 of each
of the time-of-day alarm registers are mask bits (Table 1). When all of the mask bits are logic 0, a timeof-day alarm only occurs once per week when the values stored in timekeeping registers 00h to 03h
match the values stored in the time-of-day alarm registers. An alarm is generated every day when bit 7 of
the day alarm register is set to a logic 1. An alarm is generated every hour when bit 7 of the day and hour
alarm registers is set to a logic 1. Similarly, an alarm is generated every minute when bit 7 of the day,
hour, and minute alarm registers is set to a logic 1. When bit 7 of the day, hour, minute, and seconds
alarm registers is set to a logic 1, alarm occurs every second.
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DS1305
During each clock update, the RTC compares the Alarm 0 and Alarm 1 registers with the corresponding
clock registers. When a match occurs, the corresponding alarm flag bit in the status register is set to a 1. If
the corresponding alarm interrupt enable bit is enabled, an interrupt output is activated.
Table 1. TIME-OF-DAY ALARM MASK BITS
ALARM REGISTER MASK BITS (BIT 7)
SECONDS MINUTES
HOURS
DAYS
1
1
1
1
0
1
1
1
0
0
1
1
0
0
0
1
0
0
0
0
FUNCTION
Alarm once per second
Alarm when seconds match
Alarm when minutes and seconds match
Alarm hours, minutes, and seconds match
Alarm day, hours, minutes and seconds match
SPECIAL PURPOSE REGISTERS
The DS1305 has three additional registers (control register, status register, and trickle charger register)
that control the RTC, interrupts, and trickle charger.
CONTROL REGISTER (READ 0FH, WRITE 8FH)
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
EOSC
WP
0
0
0
INTCN
AIE1
AIEO
EOSC (Enable Oscillator) – This bit when set to logic 0 starts the oscillator. When this bit is set to a
logic 1, the oscillator is stopped and the DS1305 is placed into a low-power standby mode with a current
drain of less than 100nA when power is supplied by VBAT or VCC2. On initial application of power, this bit
will be set to a logic 1.
WP (Write Protect) – Before any write operation to the clock or RAM, this bit must be logic 0. When
high, the write protect bit prevents a write operation to any register, including bits 0, 1, 2, and 7 of the
control register. Upon initial power-up, the state of the WP bit is undefined. Therefore, the WP bit should
be cleared before attempting to write to the device.
INTCN (Interrupt Control) – This bit controls the relationship between the two time-of-day alarms and
the interrupt output pins. When the INTCN bit is set to a logic 1, a match between the timekeeping
registers and the Alarm 0 registers activates the INT0 pin (provided that the alarm is enabled) and a
match between the timekeeping registers and the Alarm 1 registers activate the INT1 pin (provided that
the alarm is enabled). When the INTCN bit is set to a logic 0, a match between the timekeeping registers
and either Alarm 0 or Alarm 1 activate the INT0 pin (provided that the alarms are enabled). INT1 has no
function when INTCN is set to a logic 0.
AIE0 (Alarm Interrupt Enable 0) – When set to a logic 1, this bit permits the interrupt 0 request flag
(IRQF0) bit in the status register to assert INT0 . When the AIE0 bit is set to logic 0, the IRQF0 bit does
not initiate the INT0 signal.
AIE1 (Alarm Interrupt Enable 1) – When set to a logic 1, this bit permits the interrupt 1 request flag
(IRQF1) bit in the status register to assert INT1 (when INTCN = 1) or to assert INT0 (when INTCN = 0).
When the AIE1 bit is set to logic 0, the IRQF1 bit does not initiate an interrupt signal.
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DS1305
STATUS REGISTER (READ 10H)
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
0
0
0
0
0
0
IRQF1
IRQF0
IRQF0 (Interrupt 0 Request Flag) – A logic 1 in the interrupt request flag bit indicates that the current
time has matched the Alarm 0 registers. If the AIE0 bit is also a logic 1, the INT0 pin goes low. IRQF0 is
cleared when the address pointer goes to any of the Alarm 0 registers during a read or write.
IRQF1 (Interrupt 1 Request Flag) – A logic 1 in the interrupt request flag bit indicates that the current
time has matched the Alarm 1 registers. This flag can be used to generate an interrupt on either INT0 or
INT1 depending on the status of the INTCN bit in the control register. If the INTCN bit is set to a logic 1
and IRQF1 is at a logic 1 (and AIE1 bit is also a logic 1), the INT1 pin goes low. If the INTCN bit is set
to a logic 0 and IRQF1 is at a logic 1 (and AIE1 bit is also a logic 1), the INT0 pin goes low. IRQF1 is
cleared when the address pointer goes to any of the Alarm 1 registers during a read or write.
TRICKLE CHARGE REGISTER (READ 11H, WRITE 91H)
This register controls the trickle charge characteristics of the DS1305. The simplified schematic of Figure
3 shows the basic components of the trickle charger. The trickle-charge select (TCS) bits (bits 4–7)
control the selection of the trickle charger. To prevent accidental enabling, only a pattern of 1010 enables
the trickle charger. All other patterns disable the trickle charger. On the initial application of power, the
DS1305 powers up with the trickle charger disabled. The diode select (DS) bits (bits 2–3) select whether
one diode or two diodes are connected between VCC1 and VCC2. The resistor select (RS) bits select the
resistor that is connected between VCC1 and VCC2. The resistor and diodes are selected by the RS and DS
bits, as shown in Table 2.
Figure 3. PROGRAMMABLE TRICKLE CHARGER
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DS1305
Table 2. TRICKLE CHARGER RESISTOR AND DIODE SELECT
TCS
Bit 7
TCS
Bit 6
TCS
Bit 5
TCS
Bit 4
DS
Bit 3
DS
Bit 2
RS
Bit 1
RS
Bit 0
FUNCTION
X
X
X
X
X
X
0
0
Disabled
X
X
X
X
0
0
X
X
Disabled
X
X
X
X
1
1
X
X
Disabled
1
0
1
0
0
1
0
1
1 Diode, 2kΩ
1
0
1
0
0
1
1
0
1 Diode, 4kΩ
1
0
1
0
0
1
1
1
1 Diode, 8kΩ
1
0
1
0
1
0
0
1
2 Diodes, 2kΩ
1
0
1
0
1
0
1
0
2 Diodes, 4kΩ
1
0
1
0
1
0
1
1
2 Diodes, 8kΩ
0
1
0
1
1
1
0
0
Initial power-on state
The user determines diode and resistor selection according to the maximum current desired for battery or
super cap charging. The maximum charging current can be calculated as illustrated in the following
example. Assume that a system power supply of 5V is applied to VCC1 and a super cap is connected to
VCC2. Also assume that the trickle charger has been enabled with 1 diode and resister R1 between VCC1
and VCC2. The maximum current IMAX would, therefore, be calculated as follows:
IMAX = (5.0V - diode drop) / R1 » (5.0V - 0.7V) / 2kW » 2.2mA
As the super cap charges, the voltage drop between VCC1 and VCC2 decreases and, therefore, the charge
current decreases.
POWER CONTROL
Power is provided through the VCC1, VCC2, and VBAT pins. Three different power-supply configurations
are illustrated in Figure 4. Configuration 1 shows the DS1305 being backed up by a nonrechargeable
energy source such as a lithium battery. In this configuration, the system power supply is connected to
VCC1 and VCC2 is grounded. The DS1305 is write-protected if VCC1 is less than VBAT. The DS1305 is fully
accessible when VCC1 is greater than VBAT + 0.2V.
Configuration 2 illustrates the DS1305 being backed up by a rechargeable energy source. In this case, the
VBAT pin is grounded, VCC1 is connected to the primary power supply, and VCC2 is connected to the
secondary supply (the rechargeable energy source). The DS1305 operates from the larger of VCC1 or
VCC2. When VCC1 is greater than VCC2 + 0.2V (typical), VCC1 powers the DS1305. When VCC1 is less than
VCC2, VCC2 powers the DS1305. The DS1305 does not write-protect itself in this configuration.
Configuration 3 shows the DS1305 in battery operate mode where the device is powered only by a single
battery. In this case, the VCC1 and VBAT pins are grounded and the battery is connected to the VCC2 pin.
Only these three configurations are allowed. Unused supply pins must be grounded.
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DS1305
Figure 4. POWER SUPPLY CONFIGURATIONS
CONFIGURATION 1: BACKUP SUPPLY IS
NONRECHARGEABLE LITHIUM BATTERY
NOTE: DEVICE IS WRITE-PROTECTED IF VCC < VCCTP.
CONFIGURATION 2: BACKUP SUPPLY IS A
RECHARGEABLE BATTERY OR SUPER
CAPACITOR
NOTE: DEVICE DOES NOT PROVIDE AUTOMATIC WRITE PROTECTION.
CONFIGURATION 3: BATTERY OPERATE
MODE
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DS1305
SERIAL INTERFACE
The DS1305 offers the flexibility to choose between two serial interface modes. The DS1305 can
communicate with the SPI interface or with a standard 3-wire interface. The interface method used is
determined by the SERMODE pin. When this pin is connected to VCC, SPI communication is selected.
When this pin is connected to ground, standard 3-wire communication is selected.
SERIAL PERIPHERAL INTERFACE (SPI)
The serial peripheral interface (SPI) is a synchronous bus for address and data transfer, and is used when
interfacing with the SPI bus on specific Motorola microcontrollers such as the 68HC05C4 and the
68HC11A8. The SPI mode of serial communication is selected by tying the SERMODE pin to VCC. Four
pins are used for the SPI. The four pins are the SDO (serial data out), SDI (serial data in), CE (chip
enable), and SCLK (serial clock). The DS1305 is the slave device in an SPI application, with the
microcontroller being the master.
The SDI and SDO pins are the serial data input and output pins for the DS1305, respectively. The CE
input is used to initiate and terminate a data transfer. The SCLK pin is used to synchronize data
movement between the master (microcontroller) and the slave (DS1305) devices.
The shift clock (SCLK), which is generated by the microcontroller, is active only during address and data
transfer to any device on the SPI bus. The inactive clock polarity is programmable in some
microcontrollers. The DS1305 determines the clock polarity by sampling SCLK when CE becomes
active. Therefore, either SCLK polarity can be accommodated. Input data (SDI) is latched on the internal
strobe edge and output data (SDO) is shifted out on the shift edge (Figure 5). There is one clock for each
bit transferred. Address and data bits are transferred in groups of eight.
Figure 5. SERIAL CLOCK AS A FUNCTION OF MICROCONTROLLER CLOCK
POLARITY (CPOL)
CE
CPOL = 1
SCLK
SHIFT DATA OUT (READ)
DATA LATCH (WRITE)
SHIFT DATA OUT (READ)
DATA LATCH (WRITE)
CPOL = 0
SCLK
NOTE 1: CPHA BIT POLARITY (IF APPLICABLE) MAY NEED TO BE SET ACCORDINGLY.
NOTE 2: CPOL IS A BIT THAT IS SET IN THE MICROCONTROLLER’S CONTROL REGISTER.
NOTE 3: SDO REMAINS AT HIGH-Z UNTIL 8 BITS OF DATA ARE READY TO BE SHIFTED OUT DURING A READ.
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DS1305
ADDRESS AND DATA BYTES
Address and data bytes are shifted MSB first into the serial data input (SDI) and out of the serial data
output (SDO). Any transfer requires the address of the byte to specify a write or read to either a RTC or
RAM location, followed by one or more bytes of data. Data is transferred out of the SDO for a read
operation and into the SDI for a write operation (Figures 6 and 7).
Figure 6. SPI SINGLE-BYTE WRITE
* SCLK CAN BE EITHER POLARITY.
Figure 7. SPI SINGLE-BYTE READ
* SCLK CAN BE EITHER POLARITY.
The address byte is always the first byte entered after CE is driven high. The most significant bit (A7) of
this byte determines if a read or write takes place. If A7 is 0, one or more read cycles occur. If A7 is 1,
one or more write cycles occur.
Data transfers can occur one byte at a time or in multiple-byte burst mode. After CE is driven high an
address is written to the DS1305. After the address, one or more data bytes can be written or read. For a
single-byte transfer, one byte is read or written and then CE is driven low. For a multiple-byte transfer,
however, multiple bytes can be read or written to the DS1305 after the address has been written. Each
read or write cycle causes the RTC register or RAM address to automatically increment. Incrementing
continues until the device is disabled. When the RTC is selected, the address wraps to 00h after
incrementing to 1Fh (during a read) and wraps to 80h after incrementing to 9Fh (during a write). When
the RAM is selected, the address wraps to 20h after incrementing to 7Fh (during a read) and wraps to
A0h after incrementing to FFh (during a write).
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DS1305
Figure 8. SPI MULTIPLE-BYTE BURST TRANSFER
READING AND WRITING IN BURST MODE
Burst mode is similar to a single-byte read or write, except that CE is kept high and additional SCLK
cycles are sent until the end of the burst. The clock registers and the user RAM can be read or written in
burst mode. When accessing the clock registers in burst mode, the address pointer wraps around after
reaching 1Fh (9Fh for writes). When accessing the user RAM in burst mode, the address pointer wraps
around after reaching 7Fh (FFh for writes).
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DS1305
3-WIRE INTERFACE
The 3-wire interface mode operates similarly to the SPI mode. However, in 3-wire mode there is one I/O
instead of separate data in and data out signals. The 3-wire interface consists of the I/O (SDI and SDO
pins tied together), CE, and SCLK pins. In 3-wire mode, each byte is shifted in LSB first unlike SPI mode
where each byte is shifted in MSB first.
As is the case with the SPI mode, an address byte is written to the device followed by a single data byte
or multiple data bytes. Figure 9 illustrates a read and write cycle. In 3-wire mode, data is input on the
rising edge of SCLK and output on the falling edge of SCLK.
Figure 9. 3-WIRE SINGLE-BYTE TRANSFER
SINGLE-BYTE READ
CE
SCLK
I/O*
A0
A1
A2
A3
A4
A5 A6
0
D0
D1
D2
D3
D4
D5
D6
D7
SINGLE-BYTE WRITE
CE
SCLK
I/O*
A0
A1
A2
A3
A4
A5
A6
1
D0
D1
D2
D3
D4
D5
D6 D7
NOTE: IN BURST MODE, CE IS KEPT HIGH AND ADDITIONAL SCLK CYCLES ARE SENT UNTIL THE END OF THE BURST.
*I/O IS SDI AND SDO TIED TOGETHER.
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DS1305
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground……………………………………………..-0.5V to +7.0V
Storage Temperature Range……………………………………………………………….-55°C to +125°C
Soldering Temperature………………………………………….See IPC/JEDEC J-STD-020 Specification
This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operation
sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time can affect
reliability.
OPERATING RANGE
RANGE
Commercial
TEMP RANGE
0°C to +70°C
VCC (V)
2.0 to 5.5 VCC1 or VCC2
Industrial
-40°C to +85°C
2.0 to 5.5 VCC1 or VCC2
RECOMMENDED DC OPERATING CONDITIONS
(Over the operating range, unless otherwise specified.)
PARAMETER
Supply Voltage
VCC1, VCC2
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
7
VCC1, VCC2
2.0
5.5
V
Logic 1 Input
VIH
2.0
VCC + 0.3
V
Logic 0 Input
VIL
VBAT Battery Voltage
VCCIF Supply Voltage
VCC = 2.0V
VCC = 5V
-0.3
VBAT
VCCIF
2.0
2.0
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+0.3
+0.8
5.5
5.5
V
V
V
11
DS1305
DC ELECTRICAL CHARACTERISTICS
(Over the operating range, unless otherwise specified.)
PARAMETER
Input Leakage
Output Leakage
IOL= 1.5mA
Logic 0
Output
IOL = 4.0mA
IOH = -0.4mA
Logic 1
Output
IOH = -1.0mA
SYMBOL
MIN
-100
-1
ILI
ILO
VOL
VOH
VCC1 Active Supply Current
ICC1A
VCC1 Timekeeping Current
(Osc on)
ICC1T
VCC1 Standby Current
(Osc off)
ICC1S
VCC2 Active Supply Current
ICC2A
VCC2 Timekeeping Current
(Osc on)
ICC2T
VCC2 Standby Current
(Osc off)
Battery Timekeeping Current
Battery Standby Current
IBAT
IBATS
VCC Trip Point
VCCTP
ICC2S
VCC = 2.0V
VCC = 5V
VCCIF = 2.0V
VCCIF = 5V
VCC1 = 2.0V
VCC1 = 5V
VCC1 = 2.0V
VCC1 = 5V
VCC1 = 2.0V
VCC1 = 5V
VCC2 = 2.0V
VCC2 = 5V
VCC2 = 2.0V
VCC2 = 5V
VCC2 = 2.0V
VCC2 = 5V
VBAT = 3V
VBAT = 3V
TYP
MAX
+500
1
0.4
0.4
1.6
2.4
UNITS
µA
µA
NOTES
V
V
0.425
1.28
25.3
81
25
80
0.4
1.2
0.3
1
200
200
400
200
VBAT +
200
VBAT - 50
mA
2, 8
µA
1, 8, 12
µA
6, 8, 12
mA
2, 9
µA
1, 9, 12
nA
6, 9, 12
nA
nA
10, 12
10, 12
mV
Trickle Charge Resistors
R1
R2
R3
2
4
8
kW
Trickle Charge Diode
Voltage Drop
VTD
0.7
V
CAPACITANCE
(TA = +25°C)
PARAMETER
Input Capacitance
Output Capacitance
Crystal Capacitance
SYMBOL
CI
CO
CX
MIN
16 of 21
TYP
10
15
6
MAX
UNITS
pF
pF
pF
NOTES
DS1305
3-WIRE AC ELECTRICAL CHARACTERISTICS
(Over the operating range, unless otherwise specified.) (Figure 10 and Figure 11)
PARAMETER
SYMBOL
Data to CLK Setup
tDC
CLK to Data Hold
tCDH
CLK to Data Delay
tCDD
CLK Low Time
tCL
CLK High Time
tCH
CLK Frequency
tCLK
CLK Rise and Fall
tR, tF
CE to CLK Setup
tCC
CLK to CE Hold
tCCH
CE Inactive Time
tCWH
CE to Output High-Z
tCDZ
SCLK to Output High-Z
tCCZ
MIN
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
TYP
MAX
200
50
280
70
800
200
1000
250
1000
250
DC
0.6
2.0
2000
500
4
1
240
60
4
1
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280
70
280
70
UNITS
NOTES
ns
3,4
ns
3,4
ns
3,4,5
ns
4
ns
4
MHz
4
ns
µs
4
ns
4
µs
4
ns
3,4
ns
3,4
DS1305
Figure 10. TIMING DIAGRAM: 3-WIRE READ DATA TRANSFER
* I/O IS SDI AND SDO TIED TOGETHER.
Figure 11. TIMING DIAGRAM: 3-WIRE WRITE DATA TRANSFER
* I/O IS SDI AND SDO TIED TOGETHER.
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DS1305
SPI AC ELECTRICAL CHARACTERISTICS
(Over the operating range, unless otherwise specified.) (Figure 12 and Figure 13)
PARAMETER
SYMBOL
MIN
TYP
MAX UNITS
Data to CLK Setup
tDC
CLK to Data Hold
tCDH
CLK to Data Delay
tCDD
CLK Low Time
tCL
CLK High Time
tCH
CLK Frequency
tCLK
CLK Rise and Fall
tR, tF
CE to CLK Setup
tCC
CLK to CE Hold
tCCH
CE Inactive Time
tCWH
CE to Output High-Z
tCDZ
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
VCC = 2.0V
VCC = 5V
200
50
280
70
800
200
1000
250
1000
250
DC
0.6
2.0
2000
500
4
1
240
60
4
1
19 of 21
280
70
NOTES
ns
5,6
ns
5,6
ns
5,6,7
ns
6
ns
6
MHz
6
ns
µs
6
ns
6
µs
6
ns
5,6
DS1305
Figure 12. TIMING DIAGRAM: SPI READ DATA TRANSFER
* SCLK CAN BE EITHER POLARITY, TIMING SHOWN FOR CPOL = 1.
Figure 13. TIMING DIAGRAM: SPI WRITE DATA TRANSFER
* SCLK CAN BE EITHER POLARITY, TIMING SHOWN FOR CPOL = 1.
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DS1305
NOTES:
1) ICC1T and ICC2T are specified with CE set to a logic 0 and EOSC bit = 0 (oscillator enabled).
2) ICC1A and ICC2A are specified with CE = VCC, SCLK=2MHz at VCC = 5V; SCLK = 500kHz
at VCC = 2.0V, VIL = 0V, VIH = VCC, and EOSC bit = 0 (oscillator enabled).
3) Measured at VIH = 2.0V or VIL = 0.8V and 10ms maximum rise and fall time.
4) Measured with 50pF load.
5) Measured at VOH = 2.4V or VOL = 0.4V.
6) ICC1S and ICC2S are specified with CE set to a logic 0. The EOSC bit must be set to logic 1 (oscillator
disabled).
7) VCC = VCC1, when VCC1 > VCC2 + 0.2V (typical); VCC = VCC2, when VCC2 > VCC1.
8) VCC2 = 0V.
9) VCC1 = 0V.
10) VCC1 < VBAT.
11) VCCIF must be less than or equal to the largest of VCC1, VCC2, and VBAT.
12) Using a crystal on X1 and X2, rated for 6pF load.
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