Datasheet
Chapter 5 Resets, Interrupts, and System Configuration
MC9S08AC16 Series Data Sheet, Rev. 9
76 Freescale Semiconductor
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.
76543210
R ID7 ID6 ID5 ID4 ID3 ID2 ID1 ID0
W
Reset00010010
= Unimplemented or Reserved
Figure 5-8. System Device Identification Register — Low (SDIDL)
Table 5-9. SDIDL Register Field Descriptions
Field Description
7:0
ID[7:0]
Part Identification Number — Each derivative in the HCS08 Family has a unique identification number. The
MC9S08AC16 Series is hard coded to the value 0x012. See also ID bits in Table 5 -8.
76543210
RRTIF 0
RTICLKS RTIE
0
RTIS2 RTIS1 RTIS0
W RTIACK
Reset00000000
= Unimplemented or Reserved
Figure 5-9. System RTI Status and Control Register (SRTISC)
Table 5-10. SRTISC Register Field Descriptions
Field Description
7
RTIF
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.
6
RTIACK
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.
5
RTICLKS
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.
4
RTIE
Real-Time Interrupt Enable — This read-write bit enables real-time interrupts.
0 Real-time interrupts disabled.
1 Real-time interrupts enabled.
2:0
RTIS[2:0]
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 Tabl e 5- 11 .