Motorola MCF5281, MCF5282 user manual Exception Vector Assignments

Exception Processing Overview

Third, the processor saves the current context by creating an exception stack frame on the supervisor system stack. As a result, the exception stack frame is created at a 0-modulo-4 address on the top of the current system stack. Additionally, the processor uses a simplified fixed-length stack frame for all exceptions. The exception type determines whether the program counter placed in the exception stack frame defines the location of the faulting instruction (fault) or the address of the next instruction to be executed (next).

Fourth, the processor calculates the address of the first instruction of the exception handler. By definition, the exception vector table is aligned on a 1 Mbyte boundary. This instruction address is generated by fetching an exception vector from the table located at the address defined in the vector base register. The index into the exception table is calculated as (4 x vector number). Once the exception vector has been fetched, the contents of the vector determine the address of the first instruction of the desired handler. After the instruction fetch for the first opcode of the handler has been initiated, exception processing terminates and normal instruction processing continues in the handler.

All ColdFire processors support a 1024-byte vector table aligned on any 1 Mbyte address boundary (see Table 2-5). The table contains 256 exception vectors; the first 64 are defined by Motorola and the remaining 192 are user-defined interrupt vectors.

Table 2-5. Exception Vector Assignments

Vector	Vector	Stacked
		Program	Assignment
Number(S)	Offset (Hex)
		Counter
0	0x000	—	Initial stack pointer
1	0x004	—	Initial program counter
2	0x008	Fault	Access error
3	0x00C	Fault	Address error
4	0x010	Fault	Illegal instruction
5	0x014	Fault	Divide by zero
6–7	0x018–0x01C	—	Reserved
8	0x020	Fault	Privilege violation
9	0x024	Next	Trace
10	0x028	Fault	Unimplemented line-a opcode
11	0x02C	Fault	Unimplemented line-f opcode
12	0x030	Next	Debug interrupt
13	0x034	—	Reserved
14	0x038	Fault	Format error
15–23	0x03C–0x05C	—	Reserved
24	0x060	Next	Spurious interrupt
25–31	0x064-0x07C	—	Reserved
32–47	0x080–0x0BC	Next	Trap # 0-15 instructions
48–63	0x0C0–0x0FC	—	Reserved

MOTOROLA Chapter 2. ColdFire Core 2-11