System exceptions – Zilog Z16F2810 User Manual
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UM018809-0611
System Exceptions
ZNEO
®
CPU Core
User Manual
49
System Exceptions
System exceptions are similar to Vectored Interrupts; however, exceptions are generated
by the CPU and cannot be masked or disabled. There are five ZNEO CPU events that gen-
erate system exceptions; each is listed below and described in this chapter.
•
•
•
•
•
It is possible for individual ZNEO CPU products to generate system exceptions in addition
to those listed above.
To determine if your device generates other system exceptions, refer to the ZNEO product
specification that is specific to your device .
Following a system exception, the Flags and Program Counter are pushed on the stack.
The Program Counter value that is pushed onto the stack points to the next instruction (not
the instruction that generated the system exception).
The system exception vector is stored in a reserved memory quad at
0000_0008H
in the
nonvolatile memory space. The vector is a 32-bit pointer (service routine address) stored
in the 4-byte quad. When an exception occurs, the vector replaces the value in the Program
Counter (PC). Program execution continues with the instruction pointed to by the new PC
value.
Symbolic Operation of System Exception
A symbolic operation of system exceptions is exemplified below.
SP
SP – 1
(SP)
Flags
SP
SP – 5
(SP)
PC
PC
Vector
Note: