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Computer Group Literature Center Web Site
Falcon ECC Memory Controller Chipset
3
EDO refers to DRAMs that use an output latch on data.
Sometimes these parts are referred to as Hyper-Page
Mode DRAMs.
To ensure reliable operation, the system should always be
configured so that these two bits are encoded to match the
slowest devices that are used. Also, if any parts do not
support EDO, then these bits must set for Page Mode. The
only case in which it is permissible to set ram spd0,ram
spd1 for “50ns, EDO” is when all parts are 50ns and all
support EDO.
chipu
chipu indicates which of the two positions within the
Falcon pair is occupied by this chip. When chipu is low,
this chip is connected to the lower half of the PowerPC
60x data bus and it does not drive TA_ or AACK_. When
chipu is high, this chip is connected to the upper half of
the PowerPC 60x data bus, and it drives TA_ and AACK_.
chipu reflects the level that was on the ERCS_ pin during
power-up reset.
DRAM Attributes Register
!
Warning
To satisfy DRAM component requirements before the memory is used at
start-up, software must always wait at least 500
µ
s between the initial
setting of a bank’s size bits, to a non-zero value, and the first accessing of
that bank. These settings are in the DRAM Attributes Register (offset
$FEF80010). The delay is intended to make sure that the bank has been
refreshed at least eight times before it is used. The 500
µ
s is sufficient as
(offset $FEF80020) is within a
factor of two of matching the actual 60x clock frequency.