Freescale Semiconductor SC140 specifications Illegal

Models: SC140

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ILLEGAL

ILLEGAL

Generate an Illegal Exception

ILLEGAL

 

 

Request (AGU)

 

Operation

 

Assembler Syntax

upon service: PC → (ESP); SR → (ESP + 4);

ILLEGAL {illegal vector = $080}

SP + 8 → SP; VBA[31:12]: illegal_vector → PC;

 

 

1

→ EXP

 

 

 

111→ I[2:0]

 

 

 

1

→ ILIN

 

 

 

0

→ C

 

 

 

0

→ T

 

 

 

00 → S[1:0]

 

 

 

0

→ SLF

 

 

 

0000 → LF[3:0]

 

 

 

Description

ILLEGAL

Generates an imprecise non-maskable illegal exception request. The exact place in the execution flow that the request is serviced depends on the machine state. Imprecise means that the exception timing is not guaranteed, being asynchronous with the instruction execution. Users should not rely on any timing between the ILLEGAL instruction execution and the start of exception processing. In the most common case, the exception vector is executed after four more execution sets are executed following the illegal instruction. In other cases, it can be the set immediately after or delayed by another execution set. Thus, it should be realized that in the exception routine, the machine state cannot be reconstructed to the exact state before or after the ILLEGAL instruction is executed. It is possible, however, to know at which PC the request was raised by reading the PC_EXCP register in the EOnCE (see the EOnCE section for a description of this register).

The AGU sets the EXP bit in SR to switch the active stack pointer to the exception stack pointer. .

A-178

SC140 DSP Core Reference Manual

Page 492
Image 492
Freescale Semiconductor SC140 specifications Illegal