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Revision ID/ General Control Register
Address
Bit
Name
Operation
READ ZERO
Reset
X
REVID
aonly_en
isa_hole
adis
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$FEF80008
REVID
READ ONLY
X
The REVID bits are hard-wired to indicate the revision
level of the Falcon. The values are $01 for the first
revision, $02 for the second.
Normally, the Falcon pair responds to address-only cycles
only if they fall within the address range of one of its
enabled map decoders. When the aonly_en bit is set, the
Falcon pair also responds to address-only cycles that fall
outside of the range of its enabled map decoders provided
they are not acknowledged by some other slave within 8
clock periods. aonly_en is read-only and reflects the level
that was on the CKD4 pin at power-up reset.
When it is set, isa_hole disables any of the DRAM or
ROM/Flash blocks from responding to PowerPC accesses
in the range from $000A0000 to $000BFFFF. This has the
effect of creating a hole in the DRAM memory map for
accesses to ISA. When isa_hole is cleared, there is no hole
created in the memory map.
When adis is clear, fast page mode operation is used for
back-to-back pipelined accesses to the same page within
DRAM. When it is set, RAS is cycled between accesses.
This bit should normally be cleared unless the Falcon has
a problem operating that way.
Programming Model
3-31
3
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