Electronic Components Datasheet Search |
|
M48T35Y-70PC6TR Datasheet(PDF) 10 Page - STMicroelectronics |
|
M48T35Y-70PC6TR Datasheet(HTML) 10 Page - STMicroelectronics |
10 / 18 page M48T35, M48T35Y 10/18 CLOCK OPERATIONS Reading the Clock Updates to the TIMEKEEPER registers should be halted before clock data is read to prevent reading data in transition. Because the BiPORT TIMEKEEPER cells in the RAM array are only data registers, and not the actual clock counters, updating the registers can be halted without disturbing the clock itself. Updating is halted when a ’1’ is written to the READ bit, D6 in the Control Register 7FF8h. As long as a ’1’ remains in that position, updating is halted. After a halt is issued, the registers reflect the count; that is, the day, date, and the time that were current at the moment the halt command was issued. All of the TIMEKEEPER registers are updated si- multaneously. A halt will not interrupt an update in progress. Updating is within a second after the bit is reset to a ’0’. Setting the Clock Bit D7 of the Control Register 7FF8h is the WRITE bit. Setting the WRITE bit to a ’1’, like the READ bit, halts updates to the TIMEKEEPER registers. The user can then load them with the correct day, date, and time data in 24 hour BCD format (see Table 11). Resetting the WRITE bit to a ’0’ then transfers the values of all time registers 7FF9h- 7FFFh to the actual TIMEKEEPER counters and allows normal operation to resume.The FT bit and the bits marked as ’0’ in Table 11 must be written to ’0’ to allow for normal TIMEKEEPER and RAM operation. After the WRITE bit is reset, the next clock update will occur within one second. See the Application Note AN923 "TIMEKEEPER rolling into the 21st century" on the for information on Century Rollover. Stopping and Starting the Oscillator The oscillator may be stopped at any time. If the device is going to spend a significant amount of time on the shelf, the oscillator can be turned off to minimize current drain on the battery. The STOP bit is the MSB of the seconds register. Setting it to a ’1’ stops the oscillator. The M48T35/35Y is shipped from STMicroelectronics with the STOP bit set to a ’1’. When reset to a ’0’, the M48T35/35Y oscillator starts within 1 second. Calibrating the Clock The M48T35/35Y is driven by a quartz controlled oscillator with a nominal frequency of 32,768 Hz. The devices are tested not to exceed 35 ppm (parts per million) oscillator frequency error at 25 °C, which equates to about ±1.53 minutes per month. With the calibration bits properly set, the accuracy of each M48T35/35Y improves to better than ±4 ppm at 25 °C. The oscillation rate of any crystal changes with temperature (see Figure 10). Table 11. Register Map Address Data Function/Range BCD Format D7 D6 D5 D4 D3 D2 D1 D0 7FFFh 10 Years Year Year 00-99 7FFEh 0 0 0 10 M Month Month 01-12 7FFDh 0 0 10 Date Date: Day of Month Date 01-31 7FFCh 0 FT CEB CB 0 Day of Week Century/Day 00-01/01-07 7FFBh 0 0 10 Hours Hours (24 Hour Format) Hour 00-23 7FFAh 0 10 Minutes Minutes Minutes 00-59 7FF9h ST 10 Seconds Seconds Seconds 00-59 7FF8h W R S Calibration Control Keys: S = Sign Bit FT = Frequency Test Bit (Must be set to ‘0’ upon power for normal operation) R = Read Bit W = Write Bit ST = Stop Bit 0 = Must be set to zero CEB = Century Enable Bit CB = Century Bit Note: When CEB is set to ‘1’, CB will toggle from ‘0’ to ‘1’ or from ‘1’ to ‘0’ at the turn of the century (dependent upon the initial value set). When CEB is set to ‘0’, CB will not toggle. The WRITE Bit does not need to be set to write to CEB and CB. |
Similar Part No. - M48T35Y-70PC6TR |
|
Similar Description - M48T35Y-70PC6TR |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |