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asserted, the A31–A0, FCx, SIZx, and R/W signals are again driven to their previous
states. The MC68340 does not service interrupt requests while it is halted.
S0
S2
S4
S0
S2
S4
S0
CLKOUT
A31–A0
FC3–FC0
R/W
AS
DS
DSACKx
D15–D10
HALT
BR
BG
BGACK
READ
HALT
READ
(ARBITRATION PERMITTED
WHILE THE PROCESSOR IS
HALTED)
Figure 3-21. HALT Timing
3.5.4 Double Bus Fault
A double bus fault results when a bus error or an address error occurs during the
exception processing sequence for any of the following:
• A previous bus error
• A previous address error
• A reset
For example, the MC68340 attempts to stack several words containing information about
the state of the machine while processing a bus error exception. If a bus error exception
MOTOROLA
MC68340 USER’S MANUAL
3- 39
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