
VMEbus Mapping Example
MVME5100 Single Board Computer Programmer’s Reference (6806800H17B
)
310
Universe on the PCI Local Bus. The VME Slave Images represent the view of the Universe on the
VMEbus. The purpose of this application note is to demonstrate the process used to select the
appropriate Base and Bound values for the desired address mapping. In this case, the entire
64MB of available memory space on the board has been selected. The memory can be
segmented by selecting different sizes and mapping them using the remaining slave images
within the Universe device. In addition, by using the appropriate settings in the Control
register, the memory can be mapped as A24/D16, A16/D8, or other desired addressing.
Once the Base and Bound values are determined, the correct value for the Translate register
must be selected so that the address presented to the bus on the other side of the Universe is
correct.
Each of the Translate register’s values were determined as follows:
2700 PCI Slave Translate
In the default memory map, PCI Memory space begins at C000 0000, the first 1MB (100 0000)
is set aside for other devices on the PCI Local Bus that require PCI Memory. PowerPC addresses
from C000 0000 to DFFF FFFF are presented, zero based, on the PCI Local Bus. The Universe is
configured to accept PCI Memory addresses from 0100 0000 to 2000 0000 in PCI Slave Image
1. These addresses are passed unchanged to the VMEbus. To translate a presented PCI address
to a zero based VMEbus address, the translation value of FF00 0000 was chosen. This value is
the required translation to make the presented address (0100 0000) become 0000 0000 on
the VMEbus: 0100 0000 + FF00 0000 => 1 0000 0000.
2700 VME Slave Translate
For the VME Slave register, the Universe passes the presented address unchanged onto the PCI
Local Bus, unless translation is applied. Consulting the memory maps available in the
appropriate MVME Programmer’s Guide, one finds that PowerPC memory is located at 8000
0000 on the PCI Local bus. Thus, to translate an inbound address of 1000 0000 (the configured
VMEbus Base address of this board to 8000 0000, which is presented to DRAM as 0000 0000
and translation value of 7000 0000 is selected: 1000 0000 + 7000 0000 => 8000 0000 on the
PCI Local Bus that becomes 0000 0000 on the PowerPC bus.
5100 PCI Slave Translate
Summary of Contents for MVME5100
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