MC68HC908GP20 Datasheet, PDF (294/406 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

19.4.2 Active Resets from Internal Sources
All internal reset sources actively pull the RST pin low for 32 CGMXCLK
cycles to allow resetting of external peripherals. The internal reset signal
IRST continues to be asserted for an additional 32 cycles. See Figure
19-5. An internal reset can be caused by an illegal address, illegal
opcode, COP timeout, LVI, or POR. (See Figure 19-6.)
NOTE:
For LVI or POR resets, the SIM cycles through 4096 CGMXCLK cycles
during which the SIM forces the RST pin low. The internal reset signal
then follows the sequence from the falling edge of RST shown in Figure
19-5.
IRST
RST
CGMXCLK
IAB
RST PULLED LOW BY MCU
32 CYCLES
32 CYCLES
VECTOR HIGH
Figure 19-5. Internal Reset Timing
The COP reset is asynchronous to the bus clock.
ILLEGAL ADDRESS RST
ILLEGAL OPCODE RST
COPRST
LVI
POR
INTERNAL RESET
Figure 19-6. Sources of Internal Reset
The active reset feature allows the part to issue a reset to peripherals
and other chips within a system built around the MCU.
Advance Information
294
MC68HC908GP20 — Rev 2.1
Freescale Semiconductor