MC68HC908GR16 Datasheet, PDF (203/310 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
System Integration Module (SIM)
SIM Counter
15.3.2.5 Low-Voltage Inhibit (LVI) Reset
The low-voltage inhibit module (LVI) asserts its output to the SIM when the V_DD
voltage falls to the LVI_TRIPF voltage. The LVI bit in the SIM reset status register
(SRSR) is set, and the external reset pin (RST) is held low while the SIM counter
counts out 4096 + 32 CGMXCLK cycles.
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.
15.3.2.6 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
($FF) (see 19.3.1.1 Normal Monitor Mode). When MODRST gets asserted, an
internal reset occurs. The SIM actively pulls down the RST pin for all internal reset
sources.
15.4 SIM Counter
The SIM counter is used by the power-on reset module (POR) and in stop mode
recovery to allow the oscillator time to stabilize before enabling the internal bus
(IBUS) clocks. The SIM counter is 13 bits long.
15.4.1 SIM Counter During Power-On Reset
The power-on reset module (POR) detects power applied to the MCU. At
power-on, the POR circuit asserts the signal PORRST. Once the SIM is initialized,
it enables the clock generation module (CGM) to drive the bus clock state machine.
15.4.2 SIM Counter During Stop Mode Recovery
The SIM counter also is used for stop mode recovery. The STOP instruction clears
the SIM counter. After an interrupt, break, or reset, the SIM senses the state of the
short stop recovery bit, SSREC, in the mask option register. If the SSREC bit is a
logic 1, then the stop recovery is reduced from the normal delay of 4096 CGMXCLK
cycles down to 32 CGMXCLK cycles. This is ideal for applications using canned
oscillators that do not require long startup times from stop mode. External crystal
applications should use the full stop recovery time, that is, with SSREC cleared.
15.4.3 SIM Counter and Reset States
External reset has no effect on the SIM counter. See 15.6.2 Stop Mode for details.
The SIM counter is free-running after all reset states. See 15.3.2 Active Resets
from Internal Sources for counter control and internal reset recovery sequences.
MC68HC908GR16 — Rev. 1.0
MOTOROLA
System Integration Module (SIM)
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Data Sheet
203