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GENERAL DESCRIPTION

The DS1678 real-time clock (RTC) event recorder

records the time and date of a nonperiodic,

asynchronous event each time the INT pin is

activated. The device records the seconds, minutes,

hours, date, day of the week, month, year, and

century when the first event occurs, and starts the 16-

bit elapsed time counter (ETC). Subsequent events

trigger the recording of the ETC into the event-log

memory. This allows for up to 1025 events to be

logged. Events can be logged while the device is

operating from either V

or V

BAT

PIN CONFIGURATION

FEATURES

 Real-Time Clock/Calendar in Binary-Coded

Decimal (BCD) Format Counts Seconds,

Minutes, Hours, Date, Month, Day of the

Week, and Year with Leap Year

Compensation and is Year 2000 Compliant

 Logs Up to 1025 Consecutive Events in Read-

Only Battery-Backed Memory

 User-Programmable Event Trigger can be

Triggered by the Falling Edge, Rising Edge,

or Rising and Falling Edges of the INT Pin

 Event Counter Register Provides Data on the

Number of Events that Have Been Logged in

the Current Event-Logging Mission

 Programmable RTC Alarm

 32-Byte, Battery-Backed, General-Purpose

NV RAM



C* Serial Interface

 Three Resolution Options for Trade-Off

Accuracy vs. Maximum Time Between Events

 -40C to +85C Industrial Temperature

Range

 Underwriters Laboratory (UL) Recognized

ORDERING INFORMATION

PART

†

PIN-PACKAGE

TOP MARK

††

DS1678 8 Plastic DIP DS1678

DS1678+ 8 Plastic DIP DS1678

DS1678S 8 SO DS1678S

DS1678S+ 8 SO DS1678S

DS1678S/T&R

8 SO (Tape and

Reel)

DS1678S

DS1678S+T&R

8 SO (Tape and

Reel)

DS1678S

†

All devices are specified over the -40°C to +85°C operating

range.

††

A “‘+” anywhere on the top mark denotes a lead(Pb)-free

device.

+ Denotes a lead(Pb)-free/RoHS-compliant device.

* I

ds.

DS1678

Real-Time Event Recorder

www.maxim-ic.com

TOP VIEW

4 5

BAT

GND

INT

SCL

SDA

DS1678

PDIP (300 mils)

SO (208 mils)

TYPICAL OPERATING CIRCUIT

Summary of content (25 pages)

PAGE 1
DS1678 Real-Time Event Recorder www.maxim-ic.com GENERAL DESCRIPTION FEATURES The DS1678 real-time clock (RTC) event recorder records the time and date of a nonperiodic, asynchronous event each time the INT pin is activated. The device records the seconds, minutes, hours, date, day of the week, month, year, and century when the first event occurs, and starts the 16bit elapsed time counter (ETC). Subsequent events trigger the recording of the ETC into the event-log memory.
PAGE 2
DS1678 Real-Time Event Recorder ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin Relative to Ground……………………………………………..-0.3V to +6.0V Operating Temperature Range (noncondensing)…………………………………………...-40°C to +85°C Storage Temperature Range…………………………………………………………….…-55°C to +125°C Soldering Temperature………………………………………….
PAGE 3
DS1678 Real-Time Event Recorder AC ELECTRICAL CHARACTERISTICS (VCC= 2.6V to 5.5V or VBAT = 2.6V to 3.5V, TA = -40°C to +85°C.) (Note 1) PARAMETER SYMBOL Input Capacitance Minimum Signal Width Minimum Event Rate CONDITIONS CI MIN INT tGLITCH tEVENT TYP MAX UNITS 0.245 1.22 pF ms ms MAX UNITS 400 100 kHz 10 0.122 0.854 AC ELECTRICAL CHARACTERISTICS (VCC = 4.5V to 5.5V, TA = -40C to +85C.
PAGE 4
DS1678 Real-Time Event Recorder Note 1: Limits at -40C are guaranteed by design and not production tested. Note 2: All voltages referenced to ground. Note 3: After this period, the first clock pulse is generated. Note 4: A device must initially provide a hold time of at least 300ns for the SDA signal to bridge the undefined region of the falling edge of SCL. The maximum tHD:DAT need only be met if the device does not stretch the LOW period (tLOW) of the SCL signal.
PAGE 5
DS1678 Real-Time Event Recorder BLOCK DIAGRAM X1 CL X2 CL DIVIDER 1Hz REAL-TIME CLOCK OSCILLATOR 000h INT CONTROL LOGIC ADDRESS REGISTER USER RAM DATA LOG RAM PORT SCL SDA DATALOG NV SRAM I2C SERIAL INTERFACE Dallas Semiconductor VCC VBAT 0 DS1678 POWER CONTROL GND 5 of 25 7FFh 2048
PAGE 6
DS1678 Real-Time Event Recorder PIN DESCRIPTION PIN NAME 1, 2 X1, X2 3 VBAT 4 GND 5 SDA 6 SCL FUNCTION Connections for Standard 32.768kHz Quartz Crystal. For greatest accuracy, the DS1678 must be used with a crystal that has a specified load capacitance of 12.5pF. 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 be isolated from high-frequency signals.
PAGE 7
DS1678 Real-Time Event Recorder DETAILED DESCRIPTION The Event Counter Register contains the total number of events that have been logged in the current event-logging mission. The Event Counter Register also allows the user to determine if the data in the event-log memory has rolled over. The 16-bit ETC can be incremented once per second, once per minute, or once per hour. Each event transfers the current ETC value into the event-log memory, then clears and restarts the ETC.
PAGE 8
DS1678 Real-Time Event Recorder POWER CONTROL The device is fully accessible and data can be written and read when VCC is greater than VPF. However, when VCC falls below VPF, the internal registers are blocked from any access. The device power is switched from VCC to VBAT when VCC drops below VBAT. Operation, except for the I2C interface, is maintained from the VBAT source until VCC is returned to nominal levels (Table 1). After VCC returns above VPF, read and write access is allowed. Table 1.
PAGE 9
DS1678 Real-Time Event Recorder MEMORY The memory map in Figure 2 shows the general organization of the DS1678. As can be seen in the figure, the device memory is in one contiguous segment with a data port to access the event-log memory. Because the I2C bus is limited to a maximum of 256 addresses (one byte), the DS1678 uses the data port to access the 2048 bytes of event-log memory.
PAGE 10
DS1678 Real-Time Event Recorder The user can write only to the RTC, control registers, and user NV RAM. The rest of the memory map is read-only from the user’s perspective. During an event-log mission, all the memory is read-only. A write terminates the mission. If there is an event being recorded when the mission is terminated, the event finishes being recorded before the mission is stopped, and the values in the MIP and ME bits do not change to zeros until the mission is complete.
PAGE 11
DS1678 Real-Time Event Recorder Figure 2.
PAGE 12
DS1678 Real-Time Event Recorder EVENT LOGGING When the DS1678 event-logging function is enabled, the device is said to be on an “event-log mission” until the event logging is stopped. An event can be triggered one of three ways depending on the settings of the TRx bits in the Control Register. With the TR0 bit set to one and the TR1 bit set to zero, INT is activated on the falling edge of the input signal.
PAGE 13
DS1678 Real-Time Event Recorder Figure 3. Start Mission Flow Chart Start via External Event Start via Computer Mem Clr =1 no Clear Memory Mem Clr =1 yes no Clear Memory yes Write a 1 to the MIP bit Write a 1 to the ME bit.
PAGE 14
DS1678 Real-Time Event Recorder ROLLOVER HANDLING There are two options for dealing with the potential occurrence of a data overrun (i.e., more than 1024 total event logs in the event-log memory) (Figure 4). The first option is to enable rollovers. This is accomplished by setting the rollover bit (bit 3 of the Control Register) to one. When rollover is enabled, new data is written over previous data, starting with the Start Time Stamp Register, as if a new mission is starting.
PAGE 15
DS1678 Real-Time Event Recorder Figure 4.
PAGE 16
DS1678 Real-Time Event Recorder CLOCK, CALENDAR, AND ALARM The time and calendar information is accessed by reading/writing the appropriate register bytes. Note that some bits are set to zero. These bits always read zero regardless of how they are written. The contents of the time, calendar, and alarm registers are in the BCD format and are year 2000 compliant. The DS1678 can 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.
PAGE 17
DS1678 Real-Time Event Recorder SPECIAL-PURPOSE REGISTERS The following descriptions define the operation of the DS1678 special-purpose registers. CONTROL REGISTER (0Eh) MSB BIT 7 ME BIT 6 CLR BIT 5 DIS1 BIT 4 DIS0 BIT 3 RO BIT 2 TR1 BIT 1 TR0 LSB BIT 0 EOSC Bit 7: Mission Enable (ME). This bit enables the device to begin a mission. The ME bit cannot be written to one unless the MEM CLR bit in the Status Register is one, signifying that the memory and registers have been cleared.
PAGE 18
DS1678 Real-Time Event Recorder represents the total elapsed time since the previous event. The event counter is not incremented when the ETC rolls over because a new event has not occurred. The ETC is incremented as the selected seconds, minutes, or hours register of the RTC increments.
PAGE 19
DS1678 Real-Time Event Recorder Bit 3: Rollover (RO). This bit determines whether the data log function of the DS1678 rolls over or stops writing data to the event-log memory if the event-log memory is completely filled. If RO is set to one, the event-log memory rolls over after all 2048 bytes in the event-log memory have been used.
PAGE 20
DS1678 Real-Time Event Recorder STATUS REGISTER (0Fh) MSB BIT 7 0 BIT 6 MEM CLR BIT 5 MIP BIT 4 CM BIT 3 LOBAT BIT 2 ROF BIT 1 0 LSB BIT 0 ALMF Bit 6: Memory Cleared (MEM CLR). This bit indicates that the Event-Log Memory, Event Counter, and Start Time Stamp registers are all cleared to zero. MEM CLR is cleared to zero when an event-log mission is started (i.e., MIP = 1). Bit 5: Mission in Progress (MIP). This bit indicates the sampling status of the DS1678.
PAGE 21
DS1678 Real-Time Event Recorder EVENT COUNTER REGISTER (3Ah–3Ch) This three-byte register set provides the number of events that have been logged during the current datalogging operation (also known as a “mission”). The contents of this register can be used by software to point to the most recent data sample in the event-log memory. The data in these registers are cleared when the event-log memory is cleared.
PAGE 22
DS1678 Real-Time Event Recorder SECURITY The DS1678 provides several measures to ensure data integrity for the end user. These security measures are intended to prevent third-party intermediaries from tampering with the data that has been stored in the event-log memory. As a first security measure, the event-log memory is read-only from the perspective of the end user. The DS1678 can write the data into these memory banks, but the end user cannot write data to individual registers.
PAGE 23
DS1678 Real-Time Event Recorder A device that acknowledges must pull down the SDA line during the acknowledge clock pulse in such a way that the SDA line is stable LOW during the HIGH period of the acknowledge-related clock pulse. Of course, setup and hold times must be taken into account. A master must signal an end of data to the slave by not generating an acknowledge bit on the last byte that has been clocked out of the slave.
PAGE 24
DS1678 Real-Time Event Recorder Figure 6. Data Transfer on I2C Serial Bus SDA MSB slave address R/W direction bit acknowledgement signal from receiver acknowledgement signal from receiver 1 SCL 2 6 7 8 1 9 2 3-8 8 9 ACK ACK START CONDITION STOP CONDITION OR REPEATED START CONDITION repeated if more bytes are transferred Figure 7.
PAGE 25
DS1678 Real-Time Event Recorder CHIP INFORMATION TRANSISTOR COUNT: 110,836 PROCESS: CMOS SUBSTRATE CONNECTED TO GROUND THERMAL INFORMATION PART 8 PDIP 8 SO THETA-JA (°C/W) 110 113 THETA-JC (°C/W) 40 31 PACKAGE INFORMATION For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO.