Table 3-10. Ram Spd1,Ram Spd0 And Dram Type - Motorola MVME2600 Series Reference Manual

ram fref Some DRAMs require that they be refreshed at the rate of
7.8 s per row rather than the standard 15.6 s per row. If
any of the DRAM devices require the higher rate, then the
ram fref bit should be left set, otherwise, it can be cleared.
ram spd0,ram spd1
DRAM timing used by the Falcon pair. They are encoded
as shown:
Table 3-10. ram spd1 , ram spd0 and DRAM Type
ram spd0 , ram spd1 DRAM Speed
%00
%01
%10
%11
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.
Together ram spd0,ram spd1 control
DRAM Type
70ns Page Mode
60ns Page Mode
- Reserved
50ns EDO
Programming Model
3-35
3