MC68HC908JL3E Datasheet, PDF (82/226 Pages) Motorola, Inc – Microcontrollers

System Integration Module (SIM)
7.4 Reset and System Initialization
The MCU has these reset sources:
• Power-on reset module (POR)
• External reset pin (RST)
• Computer operating properly module (COP)
• Low-voltage inhibit module (LVI)
• Illegal opcode
• Illegal address
All of these resets produce the vector $FFFE–$FFFF ($FEFE–$FEFF in
Monitor mode) and assert the internal reset signal (IRST). IRST causes
all registers to be returned to their default values and all modules to be
returned to their reset states.
An internal reset clears the SIM counter (see 7.5 SIM Counter), but an
external reset does not. Each of the resets sets a corresponding bit in
the reset status register (RSR). (See 7.8 SIM Registers.)
7.4.1 External Pin Reset
The RST pin circuits include an internal pull-up 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 2OSCOUT cycles, assuming that the POR was not the source of the
reset. See Table 7-2 for details. Figure 7-4 shows the relative timing.
Table 7-2. PIN Bit Set Timing
Reset Type
POR
All others
Number of Cycles Required to Set PIN
4163 (4096 + 64 + 3)
67 (64 + 3)
2OSCOUT
RST
IAB PC
VECT H VECT L
Figure 7-4. External Reset Timing
Technical Data
82
MC68H(R)C908JL3E/JK3E/JK1E — Rev. 2.0
System Integration Module (SIM)
MOTOROLA