mc68hc908gp32 Freescale Semiconductor, Inc, mc68hc908gp32 Datasheet - Page 160

• Manufacturer Part Number: mc68hc908gp32
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

System Integration Module (SIM)
14.2.1 Bus Timing
In user mode, the internal bus frequency is either the crystal oscillator output (CGMXCLK) divided by four
or the PLL output (CGMVCLK) divided by four.
14.2.2 Clock Startup from POR or LVI Reset
When the power-on reset module or the low-voltage inhibit module generates a reset, the clocks to the
CPU and peripherals are inactive and held in an inactive phase until after the 4096 CGMXCLK cycle POR
timeout has completed. The RST pin is driven low by the SIM during this entire period. The IBUS clocks
start upon completion of the timeout.
14.2.3 Clocks in Stop Mode and Wait Mode
Upon exit from stop mode by an interrupt, break, or reset, the SIM allows CGMXCLK to clock the SIM
counter. The CPU and peripheral clocks do not become active until after the stop delay timeout. This
timeout is selectable as 4096 or 32 CGMXCLK cycles. (See
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.
14.3 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
14.3.1 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 CGMXCLK cycles, assuming that neither the POR nor the LVI was the source of the reset.
See
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Table 14-2
Power-on reset module (POR)
External reset pin (RST)
Computer operating properly module (COP)
Low-voltage inhibit module (LVI)
Illegal opcode
Illegal address
Reset Recovery Type
for details.
All others
POR/LVI
Figure 14-4
Table 14-2. Reset Recovery Type
MC68HC908GP32 Data Sheet, Rev. 10
shows the relative timing.
14.4 SIM
Actual Number of Cycles
Counter), but an external reset does not. Each of
4163 (4096 + 64 + 3)
67 (64 + 3)
14.6.2 Stop
Mode.)
14.7 SIM
Freescale Semiconductor
Registers.)