User`s manual

BDM-610000082 Rev A Chapter 4: Using the cpuModule 63
0Ah 10 RTC Status Register A
• Bit 7: RTC Update In Progress (Read Only) - RTC registers
should not be accessed when this bit is high. If this bit is low, you
have at least 244usec to access the RTD registers.
• Bits 6-5: Reserved
• Bit 4: CMOS Bank Selection (0 = Bank 0, 1 = Bank 1)
• Bits 3-0: Rate select for periodic interrupt.
0Bh 11 RTC Status Register B
• Bit 7: Set New Time - When high, the RTC is prevented from
updating. Set this bit before adjusting system time.
• Bit 6: Periodic Interrupt Enable - When high, the RTC IRQ will
be asserted by the periodic interrupt.
• Bit 5: Alarm Interrupt Enable - When high, the RTC IRQ will be
asserted when the current time matches the alarm time.
• Bit 4: Update Ended Interrupt Enable - When high, the RTC IRQ
will be asserted every time the RTC updates (once per second).
• Bits 2-3: Reserved
• Bit 1: Hours Byte Format - Sets the hour byte to 12 or 24 hour
time (0=12 hour, 1=24 hour). This is typically set to 24 hour
mode.
• Bit 0: Daylight Savings Enable - When high, the RTC will
automatically update itself for Daylight Savings Time. It is
recommended to leave this bit low and let the operating system
manage time zones and DST.
0Ch 12 RTC Status Register C (Read Only)
• Bit 7: IRQ Flag - Indicates that the Real Time Clock IRQ is
asserted. Goes high whenever one of the enabled interrupt
conditions in Register B occurs.
• Bit 6: Periodic Flag
• Bit 5: Alarm Flag
• Bit 4: Update Ended Flag
• Bit 3-0: Reserved
Reading this register will also clear any of set flag (IRQ, Periodic, Alarm, Update
Ended). Note that even if the interrupt source is not enabled in Register B, the
flags in Register C bits 4, 5, and 6 may still be set.
0Dh 13 RTC Status Register D
• Bit 7: Valid Time/Date
• Bit 6: Reserved
• Bits 5-0: RTC Alarm Day of the Month
32h 50 RTC Century (BDC format); if RTC Status Register A, Bit 4 = 0
48h 72 RTC Century (BDC format); if RTC Status Register A, Bit 4 = 1
Table 41 Real Time Clock Registers
Registers
(hex)
Registers
(decimal)
Function