MC9S08GB60A Datasheet, PDF (78/302 Pages) Freescale Semiconductor, Inc – HCS08 Microcontrollers

Chapter 5 Resets, Interrupts, and System Configuration
5.8.6 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 5-8. System RTI Status and Control Register (SRTISC)
0
RTIS0
0
Table 5-8. SRTISC Field Descriptions
Field
7
RTIF
6
RTIACK
5
RTICLKS
4
RTIE
2:0
RTIS[2:0]
Description
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 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 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 Period Selects — These read/write bits select the wakeup period for the RTI. One clock
source for the real-time interrupt is its own internal clock source, which oscillates with a period of approximately
t_RTI and is independent of other MCU clock sources. Using an external clock source the delays will be crystal
frequency divided by value in RTIS2:RTIS1:RTIS0. See Table 5-9.
Table 5-9. Real-Time Interrupt Period
RTIS2:RTIS1:RTIS0
Internal Clock Source ¹
(t_RTI = 1 ms, Nominal)
External Clock Source ²
Period = t_ext
0:0:0
Disable periodic wakeup timer
Disable periodic wakeup timer
0:0:1
8 ms
t_ext x 256
0:1:0
32 ms
t_ex x 1024
0:1:1
64 ms
t_ex x 2048
1:0:0
128 ms
t_ex x 4096
1:0:1
256 ms
t_ext x 8192
1:1:0
512 ms
t_ext x 16384
1:1:1
1.024 s
t_ex x 32768
1 _{See Table A-10tRTI in Appendix A, “Electrical Characteristics,” for the tolerance on these values.}
2 _{text is based on the external clock source, resonator, or crystal selected by the ICG configuration. See Table A-9 for details.}
MC9S08GB60A Data Sheet, Rev. 2
78
Freescale Semiconductor