System Integration Module (SIM)
Data Sheet
MC68HC908GR60A MC68HC908GR48A MC68HC908GR32A
210
System Integration Module (SIM)
MOTOROLA
14.3.2.2 Computer Operating Properly (COP) Reset
An input to the SIM is reserved for the COP reset signal. The overflow of the COP
counter causes an internal reset and sets the COP bit in the SIM reset status
register (SRSR) if the COPD bit in the CONFIG1 register is cleared. The SIM
actively pulls down the RST pin for all internal reset sources.
The COP module is disabled if the RST pin or the IRQ pin is held at VTST while the
MCU is in monitor mode. During a break state, VTST on the RST pin disables the
COP module.
14.3.2.3 Illegal Opcode Reset
The SIM decodes signals from the CPU to detect illegal instructions. An illegal
instruction sets the ILOP bit in the SIM reset status register (SRSR) and causes a
reset.
If the stop enable bit, STOP, in the CONFIG1 register is 0, the SIM treats the STOP
instruction as an illegal opcode and causes an illegal opcode reset. The SIM
actively pulls down the RST pin for all internal reset sources.
14.3.2.4 Illegal Address Reset
An opcode fetch from an unmapped address generates an illegal address reset.
The SIM verifies that the CPU is fetching an opcode prior to asserting the ILAD bit
in the SIM reset status register (SRSR) and resetting the MCU. A data fetch from
an unmapped address does not generate a reset. The SIM actively pulls down the
RST pin for all internal reset sources.
14.3.2.5 Low-Voltage Inhibit (LVI) Reset
The low-voltage inhibit module (LVI) asserts its output to the SIM when the VDD
voltage falls to the VTRIPF voltage. The LVI bit in the SIM reset status register
(SRSR) is set, and the external reset pin (RST) is asserted if the LVIPWRD and
LVIRSTD bits in the CONFIG1 register are 0. The RST pin will be held low while
the SIM counter counts out 4096 + 32 CGMXCLK cycles after VDD rises above
VTRIPR. Thirty-two CGMXCLK cycles later, the CPU is released from reset to allow
the reset vector sequence to occur. The SIM actively pulls down the RST pin for all
internal reset sources.
14.3.2.6 Monitor Mode Entry Module Reset (MODRST)
The monitor mode entry module reset (MODRST) asserts its output to the SIM
when monitor mode is entered in the condition where the reset vectors are erased
internal reset occurs. The SIM actively pulls down the RST pin for all internal reset
sources.