MC68HC908LJ24 Datasheet, PDF (224/464 Pages) Motorola, Inc – Microcontrollers

Real Time Clock (RTC)
The value in the chronograph data register satisfies the following
equation:
-⁽--¹---²----⁸---^H-----^z----^c---^o----^u---ⁿ---^t--^e---^r----^v---^a---^l--^u---^e-----^×-----²---⁵----⁾---+-----¹---⁶--
32
The accuracy of the chronograph counter is ±5ms (max).
12.5.5 Timebase Interrupts
In addition to the second, minute, hour, and day periodic interrupts
generated by the clock functions, the divider circuits generates four
periodic clocks, separated into two groups: 2Hz and 4Hz; 8Hz and
16Hz. The TBH bit in the RTC control register 2 (RTCCR2) selects the
group for the timebase interrupts, indicated by TB1F and TB2F flags. A
CPU interrupt request is generated if the corresponding enable bits
(TB1IE and TB2IE) are also set.
12.6 RTC Interrupts
The RTC has one alarm interrupt and seven periodic interrupts:
• Alarm interrupt
• Periodic interrupts:
– Second
– Minute
– Hour
– Day
– 1/128 seconds (chronograph)
– Timebase 1 and 2:
1/2 seconds and 1/4 seconds, or
1/8 seconds and 1/16 seconds
A CPU interrupt request is generated if the corresponding interrupt
enable bits are also set.
Data Sheet
224
Real Time Clock (RTC)
MC68HC908LJ24/LK24 — Rev. 2.1
Freescale Semiconductor