Exception Stack Frame Definition - Freescale Semiconductor MCF52277 Reference Manual

Vector
Number(s)
32–47
48–63
64–255
1
Fault refers to the PC of the instruction that caused the exception. Next refers to the PC
of the instruction that follows the instruction that caused the fault.
All ColdFire processors inhibit interrupt sampling during the first instruction of all exception handlers.
This allows any handler to disable interrupts effectively, if necessary, by raising the interrupt mask level
contained in the status register. In addition, the ISA_A+ architecture includes an instruction (STLDSR)
that stores the current interrupt mask level and loads a value into the SR. This instruction is specifically
intended for use as the first instruction of an interrupt service routine that services multiple interrupt
requests with different interrupt levels. For more details, see ColdFire Family Programmer's Reference
Manual.
3.3.3.1

Exception Stack Frame Definition

Figure 3-16 shows exception stack frame. The first longword contains the 16-bit format/vector word (F/V)
and the 16-bit status register, and the second longword contains the 32-bit program counter address.
31 30 29 28 27
→
SSP Format
+ 0x4
The 16-bit format/vector word contains three unique fields:
• A 4-bit format field at the top of the system stack is always written with a value of 4, 5, 6, or 7 by
the processor, indicating a two-longword frame format. See
• There is a 4-bit fault status field, FS[3:0], at the top of the system stack. This field is defined for
access and address errors only and written as zeros for all other exceptions. See
Freescale Semiconductor
Table 3-5. Exception Vector Assignments (continued)
Vector
Offset (Hex)
0x080–0x0BC
0x0C0–0x0FC
0x100–0x3FC
26 25 24 23 22 21 20 19 18 17
FS[3:2] Vector
Figure 3-16. Exception Stack Frame Form
Table 3-6. Format Field Encodings
Original SSP @ Time
of Exception, Bits 1:0
00
01
10
11
MCF52277 Reference Manual, Rev. 1
Stacked
Program
Counter
Next Trap # 0-15 instructions
—
Next Device-specific interrupts
16 15 14 13 12 11 10 9
FS[1:0]
Program Counter
SSP @ 1st
Instruction of Format Field
Handler
Original SSP - 8
Original SSP - 9
Original SSP - 10
Original SSP - 11
Assignment
Reserved
8 7 6 5 4
Status Register
Table 3-6.
0100
0101
0110
0111
Table
ColdFire Core
3 2 1 0
3-7.
3-17