Freescale Semiconductor MCF51QE128RM manual Exception Stack Frame Definition, Assignment, Ssp →

ColdFire Core

Table 7-6. Exception Vector Assignments (continued)

Vector	Vector	Stacked
		Program	Assignment
Number(s)	Offset (Hex)
		Counter
25–31	0x064–0x07C	—	Reserved
32–47	0x080–0x0BC	Next	Trap # 0-15 instructions
48–60	0x0C0–0x0F0	—	Reserved
61	0x0F4	Fault	Unsupported instruction
62–63	0x0F8–0x0FC	—	Reserved
64–95	0x100–0x17C	Next	Device-specific interrupts
96–102	0x180–0x198	Next	Level 1–7 software interrupts
103–255	0x19C–0x3FC	—	Reserved, unused for V1

1Fault 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_C 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. Finally, the V1 ColdFire core includes the CPUCR[IME] bit that forces the processor to automatically raise the mask level to 7 during the interrupt exception, removing the need for any explicit instruction in the service routine to perform this function. For more details, see ColdFire Family Programmer’s Reference Manual.

7.3.2.1Exception Stack Frame Definition

Figure 7-10shows 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.

SSP →

+ 0x4

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
	Format			FS[3:2]					Vector					FS[1:0]							Status Register

Program Counter

Figure 7-10. Exception Stack Frame Form

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 Table 7-7.

MCF51QE128 MCU Series Reference Manual, Rev. 3

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