MPC555
/
MPC556
U-BUS TO IMB3 BUS INTERFACE (UIMB)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
12-3
Figure 12-2 IMB Clock – Full-Speed IMB Bus
Figure 12-3 IMB Clock – Half-Speed IMB Bus
shows the number of system clock cycles that the UIMB requires to per-
form each type of bus cycle. It is assumed in this table that the IMB3 is available to the
UIMB at all times (fastest possible case).
NOTE
The UIMB interface dynamically interprets the port size of the ad-
dressed module during each bus cycle, allowing bus transfers to and
from 16-bit and 32-bit IMB modules. During a bus transaction, the
slave module on the IMB signals its port size (16- or 32-bit) via an in-
ternal port size signal.
12.4 Interrupt Operation
The interrupts from the modules on the IMB3 are propagated to the interrupt controller
in the USIU through the UIMB interface. The UIMB interrupt synchronizer latches the
Interrupts from the IMB3 and drives them onto the U-bus, where they are latched by
the USIU interrupt controller.
Table 12-2 Bus Cycles and System Clock Cycles
Bus Cycle (from U-bus Transfer Start
to U-bus Transfer Acknowledge)
Number of System Clock Cycles
Full Speed
Half Speed
Normal write
4
6
Normal read
4
6
Dynamically-sized write
6
10
Dynamically-sized read
6
10
IMB Clock
CLKOUT
T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4
B4
B1
B2
B3
B4
B1
B2
B3
IMB Clock
CLKOUT
T1
T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4
B4
B1
B2
B3
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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