SPMCK16Z4MPV20 datasheet(97/500 Pages) FREESCALE

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M68HC16 Z SERIES

CENTRAL PROCESSING UNIT

USER’S MANUAL

4-37

Total execution time is calculated using the expression:

Where:

(CLT) = Total clock periods per instruction

(CLI) = Clock periods used for internal operation

(CLP) = Clock periods used for program access

(CLO) = Clock periods used for operand access

Refer to the

CPU16 Reference Manual (CPU16RM/AD) for more information on this

topic.

4.13 Exceptions

An exception is an event that preempts normal instruction processing. Exception pro-

cessing makes the transition from normal instruction execution to execution of a rou-

tine that deals with the exception.

Each exception has an assigned vector that points to an associated handler routine.

Exception processing includes all operations required to transfer control to a handler

routine, but does not include execution of the handler routine itself. Keep the distinc-

tion between exception processing and execution of an exception handler in mind

while reading this section.

4.13.1 Exception Vectors

An exception vector is the address of a routine that handles an exception. Exception

vectors are contained in a data structure called the exception vector table, which is lo-

cated in the first 512 bytes of bank 0. Refer to Table 4-5 for the exception vector table.

All vectors except the reset vector consist of one word and reside in data space. The

reset vector consists of four words that reside in program space. Refer to SECTION 5

SYSTEM INTEGRATION MODULE for information concerning address space types

and the function code outputs. There are 52 predefined or reserved vectors, and 200

user-defined vectors.

Each vector is assigned an 8-bit number. Vector numbers for some exceptions are

generated by external devices; others are supplied by the processor. There is a direct

mapping of vector number to vector table address. The processor left shifts the vector

number one place (multiplies by two) to convert it to an address.

()

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SPMCK16Z4MPV20 Datasheet(PDF) 97 Page - Freescale Semiconductor, Inc