MC68HC08JB1 Datasheet, PDF (80/216 Pages) Motorola, Inc – Microcontrollers

8.4.1 External Pin Reset
The RST pin circuit includes an internal pullup device. Pulling the
asynchronous RST pin low halts all processing. The PIN bit of the reset
status register (RSR) is set as long as RST is held low for a minimum of
67 OSCXCLK cycles, assuming that neither the POR nor the LVI was the
source of the reset. See Table 8-2 for details. Figure 8-4 shows the
relative timing.
Table 8-2. PIN Bit Set Timing
Reset Type
POR/LVI
All others
Number of Cycles Required to Set PIN
4163 (4096 + 64 + 3)
67 (64 + 3)
OSCOUT
RST
IAB
PC
VECT H VECT L
Figure 8-4. External Reset Timing
8.4.2 Active Resets from Internal Sources
All internal reset sources actively pull the RST pin low for 32 OSCXCLK
cycles to allow resetting of external peripherals. The internal reset signal
IRST continues to be asserted for an additional 32 cycles. (See
Figure 8-5.) An internal reset can be caused by an illegal address, illegal
opcode, COP timeout, LVI, the USB module or POR. (See Figure 8-6 .
Sources of Internal Reset.)
NOTE:
For LVI or POR resets, the SIM cycles through 4096 OSCXCLK 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 8-5.
Technical Data
80
MC68HC08JB1 — Rev. 2.1
Freescale Semiconductor