MC9S08AW32CPUE Datasheet, PDF (78/324 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 5 Resets, Interrupts, and System Configuration
5.9.7 System Real-Time Interrupt Status and Control Register (SRTISC)
This register contains one read-only status flag, one write-only acknowledge bit, three read/write delay
selects, and three unimplemented bits, which always read 0.
R
W
Reset
7
RTIF
0
6
0
RTIACK
5
RTICLKS
4
RTIE
3
2
1
0
RTIS2
RTIS1
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 5-9. System RTI Status and Control Register (SRTISC)
0
RTIS0
0
Table 5-9. SRTISC Register Field Descriptions
Field
Description
7
RTIF
6
RTIACK
5
RTICLKS
4
RTIE
2:0
RTIS[2:0]
Real-Time Interrupt Flag — This read-only status bit indicates the periodic wakeup timer has timed out.
0 Periodic wakeup timer not timed out.
1 Periodic wakeup timer timed out.
Real-Time Interrupt Acknowledge — This write-only bit is used to acknowledge real-time interrupt request
(write 1 to clear RTIF). Writing 0 has no meaning or effect. Reads always return logic 0.
Real-Time Interrupt Clock Select — This read/write bit selects the clock source for the real-time interrupt.
0 Real-time interrupt request clock source is internal 1-kHz oscillator.
1 Real-time interrupt request clock source is external clock.
Real-Time Interrupt Enable — This read-write bit enables real-time interrupts.
0 Real-time interrupts disabled.
1 Real-time interrupts enabled.
Real-Time Interrupt Delay Selects — These read/write bits select the wakeup delay for the RTI. The clock
source for the real-time interrupt is a self-clocked source which oscillates at about 1 kHz, is independent of other
MCU clock sources. Using external clock source the delays will be crystal frequency divided by value in
RTIS2:RTIS1:RTIS0. See Table 5-10.
Table 5-10. Real-Time Interrupt Frequency
RTIS2:RTIS1:RTIS0
1-kHz Clock Source Delay¹
Using External Clock Source Delay
(Crystal Frequency)
0:0:0
Disable periodic wakeup timer
Disable periodic wakeup timer
0:0:1
8 ms
divide by 256
0:1:0
32 ms
divide by 1024
0:1:1
64 ms
divide by 2048
1:0:0
128 ms
divide by 4096
1:0:1
256 ms
divide by 8192
1:1:0
512 ms
divide by 16384
1:1:1
1.024 s
divide by 32768
1 _{Normal values are shown in this column based on fRTI = 1 kHz. See Appendix A, “Electrical Characteristics and Timing}
Specifications,” f_RTI for the tolerance on these values.
MC9S08AW60 Data Sheet, Rev 2
78
Freescale Semiconductor