Motorola MCU 68HC912D60 Bedienungsanleitung PDF herunterladen (Seite 7)

68HC912D60MSE4 Rev 2 7

March 14, 2001

INT: EDGE SENSITIVE IRQ DOES NOT WORK CORRECTLY DURING STOP

AR528

When using an edge sensitive IRQ signal to trigger an interrupt service routine and

the IRQ is not released during servicing, the part will not enter stop mode if the

following executed instruction is STOP.

Work-

around

When IRQ is set to be edge sensitive, release pin before executing STOP

instruction.

Wait until the transmit buffer is empty (TDRE == 1) and then disable the

transmission (Set TE == 0).

INT: WAIT CANNOT BE EXITED IF XIRQ/IRQ LEVEL DEASSERTION OCCURS

WITHIN PARTICULAR WINDOW OF TIME AR600

The device can get trapped in WAIT mode if, on exiting the WAIT instruction, the

deassertion timing of the XIRQ or level-sensitive IRQ occurs within a particular

timeframe. Only reset will allow recovery. Noise/bounce on the pins could also

cause this problem.

Work-

around

1. Use edge-triggered IRQ (IRQE=1) instead of XIRQ or level-triggered IRQ.

2. Use RTI , timer interrupts, KWU or other interrupts (except level-sensitive

IRQ or XIRQ) to exit WAIT. If using RTI, it must be enabled in WAIT

(RSWAI=0) and the COP must be disabled (CME=0).

3. Assert XIRQ or level-sensitive IRQ until the interrupt subroutine is entered.

4. Add de-bouncing logic to prevent inadvertent highs when exiting WAIT.

INT: DISABLING INTERRUPT WITH I MASK BIT CLEAR CAN CAUSE SWI

AR527

If the source of an interrupt is taken away by disabling the interrupt without setting

the I mask bit in the CCR, an SWI interrupt may be fetched instead of the vector for

the interrupt source that was disabled.

Work-

around

Before disabling an interrupt using a local interrupt control bit, set the I mask bit in

the CCR.

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Motorola MCU 68HC912D60 Bedienungsanleitung Seite 7