MC68340 datasheet(179/441 Pages) FREESCALE

179 / 441 page

5- 42

MC68340 USER’S MANUAL

MOTOROLA

When the CPU32 completes exception processing, it is ready to begin either exception

processing for a pending exception or execution of a handler routine. Priority assignment

governs the order in which exception processing occurs, not the order in which exception

handlers are executed.

Table 5-17. Exception Priority Groups

Group/

Priority

Exception and

Relative Priority

Characteristics

Reset

Aborts all processing (instruction or

exception); does not save old context.

1.1

1.2

Address Error

Bus Error

Suspends processing (instruction or

exception); saves internal context.

BKPT#n, CHK, CHK2,

Division by Zero, RTE,

TRAP#n, TRAPcc, TRAPV

Exception processing is a part of

instruction execution.

Illegal Instruction, Line A,

Unimplemented Line F,

Privilege Violation

Exception processing begins before

instruction execution.

4.1

4.2

4.3

Trace

Hardware Breakpoint

Interrupt

Exception processing begins when current

instruction or previous exception

processing is complete.

As a general rule, when simultaneous exceptions occur, the handler routines for lower

priority exceptions are executed before the handler routines for higher priority exceptions.

For example, consider the arrival of an interrupt during execution of a TRAP instruction,

while tracing is enabled. Trap exception processing (2) is done first, followed immediately

by exception processing for the trace (4.1), and then by exception processing for the

interrupt (4.3). Each exception places a new context on the stack. When the processor

resumes normal instruction execution, it is vectored to the interrupt handler, which returns

to the trace handler that returns to the trap handler.

There are special cases to which the general rule does not apply. The reset exception will

always be the first exception handled since reset clears all other exceptions. It is also

possible for high-priority exception processing to begin before low-priority exception

processing is complete. For example, if a bus error occurs during trace exception

processing, the bus error will be processed and handled before trace exception

processing is completed.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

MC68340 Datasheet(PDF) 179 Page - Freescale Semiconductor, Inc

MC68340 Datasheet(HTML) 179 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL