U-Bus to IMB3 Bus Interface (UIMB)
MPC561/MPC563 Reference Manual, Rev. 1.2
12-2
Freescale Semiconductor
WARNING
The user should not perform instruction fetches from modules on the IMB3.
12.2
UIMB Block Diagram
Figure 12-1. UIMB Interface Module Block Diagram
12.3
Clock Module
The clock module within the UIMB interface generates the IMB3 clock. The IMB3 clock is the main
timing reference used within the IMB3 modules.
The IMB3 clock is generated based on the STOP and HSPEED bits in the UIMB module configuration
register (UMCR). If the STOP = 1, the IMB3 clock is not generated. If the STOP = 0 and the HSPEED =
0, the IMB3 clock is generated as the inversion of the internal system clock. This is the same frequency as
the CLKOUT if SCCR[EBDF] = 0b00 – full speed external bus. (See
.) If the HSPEED = 1,
then the IMB3 clock is one-half of the internal system frequency. (See
.)
Table 12-1. STOP and HSPEED Bit Functionality
STOP
HSPEED
Functionality
0
0
IMB3 bus frequency is the same as U-bus frequency.
0
1
IMB3 bus frequency is half that of the U-bus frequency.
1
X
IMB3 clock is not generated.
Address
Decode
Data
Mux
Interrupt
Synchronizer
Scan Control
U-bus
Interface
IMB3
Interface
Clock Control
U-bus
IMB3
Summary of Contents for MPC561
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