MPC555
/
MPC556
U-BUS TO IMB3 BUS INTERFACE (UIMB)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
12-4
12.4.1 Interrupt Sources and Levels on IMB
The IMB3 has eight interrupt lines. There can be a maximum of 32 levels of interrupts
from the modules on IMB bus. A single module can be a source for more than one in-
terrupt
.
For example, the QSMCM can generate two interrupts (one for QSCI1/QSCI2
and another for QSPI). In this case, the QSMCM has two interrupt sources. Each of
these two sources can assert the interrupt on any of the 32 levels.
It is possible for multiple interrupt sources to assert the same interrupt level
.
To reduce
the latency, it is a good practice for each interrupt source to assert an interrupt on a
level on which no other interrupt source is mapped.
12.4.2 IMB Interrupt Multiplexing
The IMB has 10 lines for interrupt support. Eight lines are for interrupts and two for
ILBS. These lines will transfer the 32 interrupt levels to the interrupt synchronizer. A
diagram of the interrupt flow is shown in
Figure 12-4 Interrupt Synchronizer Signal Flow
Latching 32 interrupt levels using eight IMB interrupt lines is accomplished with a 4:1
time-multiplexing scheme. The UIMB drives two signals (ILBS[0:1]) with a multiplexer
select code that tells all interrupting modules on the IMB about which group of signals
to drive during the next clock.
12.4.3 ILBS Sequencing
The IMB interface drives the ILBS signals continuously, incrementing through a code
sequence (00, 01, 10, 11) once every clock The IRQMUX[0:1] bits in the IMB module
configuration register select which type of multiplexing the Interrupt synchronizer will
perform. The IRQMUX field can select time-multiplexing protocols for 8, 16, 24 or 32
interrupt sources
.
These protocols would take one, two, three or four clocks, respec-
tively.
UIPEND
IMB interrupt
8
Block
Byte Count
Byte-enables
(24:31)
(16:23)
(8:15)
(0:7)
8
to IMB
Byte-enable
2
4
U-bus Interrupt
U-bus Data[0:31]
Level[0:7]
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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