M68HC08 datasheet(107/332 Pages) FREESCALE

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System Integration Module (SIM)

MC68HC908JB16 — Rev. 1.1

Technical Data

Freescale Semiconductor

System Integration Module (SIM)

107

8.5 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 also serves as

a prescaler for the computer operating properly module (COP). The SIM

counter uses 12 stages for counting, followed by a 13th stage that

triggers a reset of SIM counters and supplies the clock for the COP

module. The SIM counter is clocked by the falling edge of OSCDCLK.

8.5.1 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 oscillator to drive the bus clock state machine.

Table 8-3. Registers not Affected by Normal Reset

Bits

Registers

After Reset

(except POR or

LVI)

After POR or LVI

LVIDR, LVI5OR3,

URSTD, LVID

CONFIG

Unaffected

USBEN

UADDR

Unaffected

PULLEN

UCR3

Unaffected

All

USR0, USR1

Unaffected

Indeterminate

All

UE0D0–UE0D7

Unaffected

Indeterminate

All

UE1D0–UE1D7

Unaffected

Indeterminate

All

UE2D0–UE2D7

Unaffected

Indeterminate

All

PTA, PTC, PTD,

and PTE

Unaffected

Indeterminate

DDRA7

DDRA

Unaffected

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