DS1678 Maxim, DS1678 Datasheet
DS1678
Available stocks
Related parts for DS1678
DS1678 Summary of contents
Page 1
... 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) ...
Page 2
... 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 above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect device reliability. ...
Page 3
AC ELECTRICAL CHARACTERISTICS (V = 2. 2.6V to 3.5V BAT PARAMETER SYMBOL Input Capacitance Minimum Signal Width Minimum Event Rate AC ELECTRICAL CHARACTERISTICS (V = 4.5V to 5.5V -40C to +85C.) ...
Page 4
... 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 t HD:DAT Note 5: A fast-mode device can be used in a standard-mode system, but the requirement t automatically the case if the device does not stretch the LOW period of the SCL signal ...
Page 5
... BLOCK DIAGRAM OSCILLATOR CONTROL INT LOGIC SCL SERIAL SDA INTERFACE V CC POWER V BAT CONTROL GND 1Hz DIVIDER REAL-TIME CLOCK ADDRESS USER RAM REGISTER DATA LOG RAM PORT Dallas Semiconductor DS1678 000h 0 DATALOG NV SRAM 7FFh 2048 ...
Page 6
... INT pin, a rising edge both the rising and falling edges. 7 INT The INT pin can also be used as an output when the DS1678 is not in an event-logging mission. The INT pin becomes an output and generates an alarm interrupt if the DISx bits are set to zero and the RTC reaches the preset value in the alarm register ...
Page 7
... Alarm Trip Point Register is reached. The flag is readable via the I during an event-logging mission or, when the DS1678 is not in a mission, INT becomes an output and generates an alarm interrupt if the value in the RTC equals the value in the RTC Alarm Register and the duration interval select (DISx) bits are both set to zeros ...
Page 8
... PF CC BAT OSCILLATOR CIRCUIT The DS1678 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or capacitors ( operate. Table 2 specifies several crystal parameters for the external crystal, L and the oscillator block in the Block Diagram shows a functional schematic of the oscillator circuit. Using a crystal with the specified characteristics, the startup time is usually less than one second ...
Page 9
... 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. 2 Because the I C 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
... During an event-log mission, memory locations 30h and above are not accessible to the user to avoid data collisions from a user read and an event being logged at the same time. If the user tries to read a location with an address greater than 2Fh during a mission, the value returned is 00h. Table 3. DS1678 Event Elapsed Time Duration ADDRESS REGISTE 0000 ...
Page 11
... Figure 2. DS1678 RTC and Control Page MSB ADDRESS BIT 7 BIT 12/ Year 07 10 Century Seconds Alarm Minutes Alarm 0A MH 12/ CLR MEM 0F 0 CLR ↓ 2F Higher addresses read back as 00h while a mission is in progress. ...
Page 12
... EVENT LOGGING When the DS1678 event-logging function is enabled, the device is said “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
Figure 3. Start Mission Flow Chart Start via Computer Mem Clr =1 yes Write the MIP bit The ME bit is Automatically Written Time/Date Stamp is Written ETC Starts Incrementing EC is Incremented no ...
Page 14
... The address pointer points to the oldest data in the event-log memory, and, if the memory has rolled over at least one time, the rollover flag is set to one. The DS1678 has been designed so the user cannot directly write to the event-log memory. This prevents writing invalid data to the event-log registers ...
Page 15
Figure 4. Rollover Flow Chart EC is Incremented INT Input Activated Memory Full Rollover Enable = 1 ETC Written to Event 0 and Time/Date Stamp is Written ETC is Cleared no Continue to Monitor Input yes no Record Event in ...
Page 16
... 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. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is the AM/PM bit with logic one being PM. In the 24-hour mode, bit 5 is the second 10-hour bit (20– ...
Page 17
... Time Stamp Register, the Event 0 Rollover Stamp is written to zero, the Event Counter Register is incremented, and the ETC begins incrementing. When the ME bit is set to logic zero, the DS1678 waits until a one is written to the MIP bit via the I interface to start the mission. When the MIP bit is written to one, the ME bit is set to one, the current time/date is recorded in the Start Time Stamp register, the Event 0 Rollover Stamp is written to zero, the Event Counter Register is incremented, and the ETC begins incrementing ...
Page 18
... The largest interval between events that can be accurately measured without using additional memory space and reducing the total number of events able to be logged is 65,535 seconds, or about 18.2 hours. If the maximum time between events could be greater than 18.2 hours, consider using one of the courser resolutions to conserve memory ...
Page 19
... 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 set to one, the event-log memory rolls over after all 2048 bytes in the event-log memory have been used. After the ...
Page 20
... 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. If MIP is logic one, the device is currently on a “mission” in which it is operating in the event-logging mode. The MIP bit is changed to logic one immediately following the activation of INT if the ME bit of the Control Register contains a one ...
Page 21
... This means that the minimum event occurrence that can be recognized by the DS1678 requires seven to 10 internal clock cycles (0.854ms to 1.22ms). Failure to ensure this timing causes the event to be ignored. Thus recommended that you design with the maximum timing specs ...
Page 22
... 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. This prevents an unscrupulous intermediary from writing false data to the DS1678. The end user, however, can clear the contents of the event-log memory ...
Page 23
... However, in this mode, the direction bit indicates that the transfer direction is reversed. Serial data is transmitted on SDA by the DS1678 while the serial clock is input on SCL. The slave address byte is the first byte received after the master generates a START condition. The address byte contains the 7-bit DS1678 address, which is 1001010, followed by the direction bit (R/W), which is 1 ...
Page 24
... Figure 6. Data Transfer on I SDA MSB slave address SCL 1 2 START CONDITION 2 Figure Serial Communication with DS1678 W rite vic yte ...
Page 25
... The Maxim logo is a registered trademark of Maxim Integrated Products, Inc. The Dallas logo is a registered trademark of Dallas Semiconductor Corporation. THETA-J C (°C/ DOCUMENT NO. 21-0043 21-0262 © 2005 Maxim Integrated Products DS1678 Real-Time Event Recorder ...