Motorola MC68020 - Exception Stack Frame

2- 6 M68020 USER’S MANUAL MOTOROLA
2.3.2 Exception Stack Frame
Exception processing saves the most volatile portion of the current processor context on
the top of the supervisor stack. This context is organized in a format called the exception
stack frame. This information always includes a copy of the SR, the PC, the vector offset
of the vector, and the frame format field. The frame format field identifies the type of stack
frame. The RTE instruction uses the value in the format field to properly restore the
information stored in the stack frame and to deallocate the stack space. The general form
of the exception stack frame is illustrated in Figure 2-1. Refer to Section 6 Exception
Processing for a complete list of exception stack frames.
0
15
SS
P
12
FORMAT
S
TATUS REGISTE
R
PROGRAM COUNTER
V
ECTOR OFFSE
T
A
DDITIONAL PROCESSOR STATE INFORMATIO
N
(2, 6, 12, OR 42 WORDS, IF NEEDED)
Figure 2-1. General Exception Stack Frame