Assertion Of Ipend; Interrupt Acknowledge Termination Summary - Motorola M68060 User Manual

Bus Operation
instruction boundary (following any higher priority exception). The IPEND signal negates
after the interrupt acknowledge bus cycle.
IPL2–IPL0
IPLx RECOGNIZED
COMPARE REQUEST WITH MASK IN SR
IPEND is intended to provide status information, and must not be used to replace the inter-
rupt acknowledge cycle. As such, normal applications do not rely on IPEND to disable inter-
rupts. Applications that use IPEND as a replacement for the interrupt acknowledge cycle are
neither recommended nor supported.
The MC68060 takes an interrupt exception for a pending interrupt within one instruction
boundary after processing any other pending exception with a higher priority. Thus, the
MC68060 executes at least one instruction in an interrupt exception handler before recog-
nizing another interrupt request. The following paragraphs describe the various kinds of
interrupt acknowledge bus cycles that can be executed as part of interrupt exception pro-
cessing. Table 7-4 provides a summary of the possible interrupt acknowledge terminations
and the exception processing results. Note that TRA must always be negated for proper
operation in the MC68040 acknowledge termination mode.
Table 7-4. Interrupt Acknowledge Termination Summary
Acknowledge
Termination TA
Mode
Either High
MC68040 High
Native-MC68060 Don't Care
Either Low
Either Low
MC68040 Low
Native-MC68060 Don't Care
MC68040 Don't Care Don't Care
7-34
CLK
IPEND
IPLx SYNCHRONIZED
Figure 7-26. Assertion of IPEND
TEA TRA
High High
Low High
Low Don't Care Don't Care
High High
High High
Low High
High Low
Low
M68060 USER'S MANUAL
ASSERT IPEND
AVEC Termination Condition
Don't Care Insert Wait States
Don't Care
Take Spurious Interrupt Exception
Register Vector Number on D7–D0 and Take Inter-
High
rupt Exception
Low Take Autovectored Interrupt Exception
Don't Care
Retry Interrupt Acknowledge Cycle
Don't Care
Don't Care Illegal Combination, Unsupported
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