mc68ec060 Freescale Semiconductor, Inc, mc68ec060 Datasheet - Page 206

• Manufacturer Part Number: mc68ec060
• Description: Mc68060 Superscalar 68k Microprocessor Including The Lc060 And Ec060
• Manufacturer: Freescale Semiconductor, Inc

7.9.3 Double Bus Fault
A double bus fault occurs when an access or address error occurs during the exception pro-
cessing sequence, e.g., the processor attempts to stack several words containing informa-
tion about the state of the machine while processing an access error exception. If a bus error
occurs during the stacking operation, the second error is considered a double bus fault and
the processor is halted.
The MC68060 indicates a double bus fault condition by continuously driving PSTx with an
encoded value of $1C until the processor is reset. Only an external reset operation can
restart a halted processor. The halted processor releases the external bus by negating BR
and forcing all outputs to a high-impedance state.
MOTOROLA
NATIVE-MC68060
ACKNOWLEDGE
ACKNOWLEDGE
TERMINATION
TERMINATION
MISCELLANEOUS
MC68040
MODE
MODE
ATTRIBUTES
SIZ1–SIZ0
A31–A0
D31–D0
BCLK
Figure 7-40. Line Write Retry Bus Cycle Timing
R/W
TEA
TEA
TIP
SAS
TRA
TRA
TS
TA
TA
C1
SIGNALED
RETRY
M68060 USER’S MANUAL
LINE
C2
C1
C2
RETRY CYCLE
C3
C4
C5
Bus Operation
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