MC68LC040RC25A Datasheet, PDF (237/442 Pages) Freescale Semiconductor, Inc – M68040 Users Manual

Freescale Semiconductor, Inc.
8.4.6 Access Error Stack Frame (Format $7)
A 30-word access error stack frame is created for data and instruction access faults other
than instruction address errors. In addition to information about the current processor
status and the faulted access, the stack frame also contains pending write-backs that the
access error exception handler must complete. The following paragraphs describe in
detail the format for this frame and how the processor uses it when returning from
exception processing.
Stack Frames
15
0
SP
STATUS REGISTER
+$02
PROGRAM COUNTER
+$06
+$08
+$0A
+$0C
+$0E
+$10
+$12
+$14
0111
VECTOR OFFSET
EFFECTIVE ADDRESS (EA)
SPECIAL STATUS WORD (SSW)
$00
WRITE-BACK 3 STATUS (WB3S)
$00
WRITE-BACK 2 STATUS (WB2S)
$00
WRITE-BACK 1 STATUS (WB1S)
FAULT ADDRESS (FA)
+$18
WRITE-BACK 3 ADDRESS (WB3A)
+$1C
WRITE-BACK 3 DATA (WB3D)
+$20
WRITE-BACK 2 ADDRESS (WB2A)
+$24
WRITE-BACK 2 DATA (WB2D)
+$28
WRITE-BACK 1 ADDRESS (WB1A)
+$2C
WRITE-BACK 1 DATA/PUSH DATA LW0 (WB1D/PD0)
+$30
PUSH DATA LW 1 (PD1)
+$34
PUSH DATA LW 2 (PD2)
+$38
PUSH DATA LW 3 (PD3)
Exception Types
• Data or Instruction Access
Fault (ATC Fault or Bus
Error)
Stacked PC Points To
• Next Instruction
ACCESS ERROR STACK FRAME
(30 WORDS)–FORMAT $7
8.4.6.1 EFFECTIVE ADDRESS. The effective address contains address information when
one of the continuation flags CM, CT, CU, or CP in the SSW is set.
8.4.6.2 SPECIAL STATUS WORD (SSW). The SSW information indicates whether an
access to the instruction stream or the data stream (or both) caused the fault and contains
status information for the faulted access. Figure 8-7 illustrates the SSW format.
15 14 13 12 11 10 9
8
7
CP CU CT CM MA ATC LK RW X
6
5
SIZE
4
3
TT
2
1
0
TM
Figure 8-7. Special Status Word Format
8-24
M68040 USER’S MANUAL
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