Programming Model
http://www.motorola.com/computer/literature
3-45
3
Scrub/Refresh Register
scb0,scb1
These bits increment every time the scrubber completes a
scrub of the entire DRAM. When these bits reach binary
11, they roll over to binary 00 and continue. These bits are
cleared by power-up reset.
swen
When set, swen allows the scrubber to perform write
cycles. When cleared, swen prevents scrubber writes.
rtest0,1,2
The rtest bits enable certain refresh counter test modes.
Table 3-12 shows their encodings. Note that these test
modes are not intended to be used once the chip is in a
system.
ADDRESS
$FEF80040
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
sc
b0
sc
b1
0
0
0
0
0
sw
e
n
0
0
0
0
0
rtes
t0
rtes
t1
rtes
t2
OPERATION
R
R
R
R
R
R
R
R/W
R
R
R
R
R
R/W
R/W
R/W
READ ZERO
READ ZERO
RESET
0 P
0 P
X
X
X
X
X
0 P
X
X
X
X
X
0 P
0 P
0 P
X
X
Table 3-12. rtest encodings
rtest0,rtest1,rtest2
Test Mode selected
%000
Normal Counter Operation
%001
RA counts at 16x
%010
RA counts at 256x
%011
RA is always at roll value for CA
%100
CA counts at 16x
%101
CA counts at 256x
%110
reserved
%111
reserved