Programming Model
http://www.motorola.com/computer/literature
3-35
3
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 8 times before it is used. The 500
µ
s is sufficient as long
as the CLK Frequency Register (offset $FEF80020) is within a factor of 2
of matching the actual 60x clock frequency
ram a/b/c/d en ram a/b/c/d en enables accesses to the corresponding
block of DRAM when set, and disables them when cleared.
Address
$FEF80010
Bit
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Name
ra
m a
e
n
0
0
0
0
ra
m a
si
z0
ra
m a
si
z1
ra
m a
si
z2
ra
m b e
n
0
0
0
0
ra
m b si
z0
ra
m b si
z1
ra
m b si
z2
ra
m c
e
n
0
0
0
0
ra
m c
si
z0
ra
m c
si
z1
ra
m c
si
z2
ra
m d e
n
0
0
0
0
ra
m d si
z0
ra
m d si
z1
ra
m d si
z2
Operation
R/W
R
R
R
R
R/W
R/W
R/W R/W
R
R
R
R
R/W
R/W
R/W R/W
R
R
R
R
R/W
R/W
R/W
R/W
R
R
R
R
R/W
R/W
R/W
Reset
0 P
L
X
X
X
X
0 P
0 P
0 P 0 P
L
X
X
X
X
0 P
0 P
0 P 0 P
L
X
X
X
X
0 P
0 P
0 P
0 P
L
X
X
X
X
0 P
0 P
0 P