mc68hc908lb8 Freescale Semiconductor, Inc, mc68hc908lb8 Datasheet - Page 174

• Manufacturer Part Number: mc68hc908lb8
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

System Integration Module (SIM)
In wait mode, the CPU clocks are inactive. The SIM also produces two sets of clocks for other modules.
Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode.
Some modules can be programmed to be active in wait mode.
17.3 Reset and System Initialization
The MCU has these reset sources:
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
the resets sets a corresponding bit in the SIM reset status register (SRSR). See
17.3.1 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 SIM reset status register (SRSR) is set as long as RST is held low for a
minimum of 67 BUSCLKX4 cycles, assuming that neither the POR nor the LVI was the source of the reset.
See
17.3.2 Active Resets from Internal Sources
All internal reset sources actively pull the RST pin low for 32 BUSCLKX4 cycles to allow resetting of
external peripherals. The internal reset signal IRST continues to be asserted for an additional 32 cycles.
174
•
•
•
•
•
•
•
Table 17-2
Power-on reset module (POR)
External reset pin (RST)
Computer operating properly module (COP)
Low-voltage inhibit module (LVI)
Illegal opcode
Illegal address
Forced monitor mode entry reset (MODRST)
BUSCLKX2
RST
IAB
for details.
PC
Reset Type
All others
POR/LVI
Figure 17-4
Figure 17-4. External Reset Timing
Table 17-2. PIN Bit Set Timing
MC68HC908LB8 Data Sheet, Rev. 1
shows the relative timing.
Number of Cycles Required to Set PIN
17.4 SIM
4163 (4096 + 64 + 3)
Counter), but an external reset does not. Each of
67 (64 + 3)
VECT H VECT L
17.7 SIM Registers.
Freescale Semiconductor