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M48T86 Fiches technique(PDF) 6 Page - STMicroelectronics |
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M48T86 Fiches technique(HTML) 6 Page - STMicroelectronics |
6 / 23 page M48T86 6/23 Table 3. Time, Calendar and Alarm Formats Address RTC Bytes Range Decimal Binary BCD 0 Seconds 0-59 00-3B 00-59 1 Seconds Alarm 0-59 00-3B 00-59 2 Minutes 0-59 00-3B 00-59 3 Minutes Alarm 0-59 00-3B 00-59 4 Hours, 12-hrs 1-12 01-0C AM 81-8C PM 01-12 AM 81-92 PM Hours, 24-hrs 0-23 00-17 00-23 5 Hours Alarm, 12-hrs 1-12 01-0C AM 81-8C PM 01-12 AM 81-92 PM Hours Alarm, 24-hrs 0-23 00-17 00-23 6 Day of Week (1 = Sun) 1-7 01-07 01-07 7 Day of Month 1-31 01-1F 01-31 8 Month 1-12 01-0C 01-12 9 Year 0-99 00-63 00-99 TIME, CALENDAR, AND ALARM LOCATIONS The time and calendar information is obtained by reading the appropriate memory bytes. The time, calendar, and alarm registers are set or initialized by writing the appropriate RAM bytes. The con- tents of the time, calendar, and alarm bytes can be either Binary or Binary-Coded Decimal (BCD) for- mat. Before writing the internal time, calendar, and alarm register, the SET bit (Register B; Bit 7) should be written to a logic "1". This will prevent updates from occurring while access is being at- tempted. In addition to writing the time, calendar, and alarm registers in a selected format (binary or BCD), the Data Mode (DM) bit (Register B; Bit 2), must be set to the appropriate logic level ("1" sig- nifies binary data; "0" signifies Binary Coded Dec- imal (BCD data). All time, calendar, and alarm bytes must use the same data mode. The SET bit should be cleared after the Data Mode bit has been written to allow the Real Time Clock to up- date the time and calendar bytes. Once initialized, the Real Time Clock makes all updates in the se- lected mode. The data mode cannot be changed without reinitializing the ten data bytes. Table 3 shows the binary and BCD formats of the time, cal- endar, and alarm locations. The 24/12 bit (Regis- ter B; Bit 1) cannot be changed without reinitializing the hour locations. When the 12-hour format is selected, a logic one in the high order bit of the hours byte represents PM. The time, calen- dar, and alarm bytes are always accessible be- cause they are double buffered. Once per second the ten bytes are advanced by one second and checked for an alarm condition. If a read of the time and calendar data occurs during an update, a problem exists where seconds, minutes, hours, etc. may not correlate. However, the probability of reading incorrect time and calendar data is low. Methods of avoiding possible incorrect time and calendar reads are reviewed later in this text. NON-VOLATILE RAM The 114 general purpose non-volatile RAM bytes are not dedicated to any special function within the M48T86. They can be used by the processor pro- gram as non-volatile memory and are fully acces- sible during the update cycle. |
Numéro de pièce similaire - M48T86 |
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Description similaire - M48T86 |
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