mcf5407 Freescale Semiconductor, Inc, mcf5407 Datasheet - Page 447

• Manufacturer Part Number: mcf5407
• Description: Mcf5407 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

18.7.2 Interrupt-Acknowledge Cycle
When the MCF5407 processes an interrupt exception, it performs an interrupt-
acknowledge bus cycle to obtain the vector number that contains the starting location of the
interrupt exception handler. The interrupt-acknowledge bus cycle is a read transfer that
differs from normal read cycles in the following respects:
During the interrupt-acknowledge bus cycle (a read cycle), the responding device places the
vector number on D[31:24] and the cycle is terminated normally with TA. Figure 18-23 is
a flow diagram for an interrupt-acknowledge cycle terminated with TA.
• The interrupt request on the interrupt control pins is raised to level 7 and stays there
• The interrupt request on the interrupt control pins is raised to level 7 and stays there.
• TT[1:0] = 0x3 to indicate a CPU space or acknowledge bus cycle.
• TM[2:0] = the level of interrupt being acknowledged.
• A[31:5] = 0x7F_FFFF.
• A[4:2] = the interrupt request level being acknowledged (same as TM[2:0]).
• A[1:0] = 00.
until an interrupt-acknowledge cycle begins. The level later drops but then returns to
level 7, causing a second transition on the interrupt control lines.
If the level 7 interrupt routine lowers the mask level, a second level 7 interrupt is
recognized without a transition of the interrupt control pins. After the level 7 routine
completes, the MCF5407 compares the mask level to the request level on the IRQx
signals. Because the mask level is lower than the requested level, the interrupt mask
is set back to level 7. To ensure it is recognized, the level 7 request on IRQ7 must be
held until the second interrupt-acknowledge bus cycle begins.
Chapter 18. Bus Operation
Interrupt Exceptions
18-19