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2-18 Theory of Operation
HEALER CAM
HEALER RAM
(ADDRESS)
(DATA)
0
31
0
31 32
39
I
1
0
I
DATA
CHECK
1
0
BITS
11
1 1
•
•
•
•
•
•
1
31
......
1
31
/
......
......
...... ......
/
...... ......
......
/
...... ......
......
(
0
...... ......
10 11
12
13
14 15
21 22
2930
J
Y ADDRESS
X ADDRESS
CS3 (7 BITS)
(8 BITS)
r
A.
,
PHYSICAL MEMORY ADDRESS
1=HEALED LOCATION
I~
(19 BITS)
~l
X-DON'T CARE
Figure
2-8. 256K
Memory Healing
Memory Organization - 512K Byte RAM Board
The 512K
RAM
board is similar to the 256K
RAM
finstrate. The board itself is a polyimide board
instead of a finstrate.
It
contains twice as many
RAM
chips on the board as the 256K
RAM
board
(Figure 2-9). The
RAM
chips are the same as used on the 256K byte board.
The
Me
on the
RAM
board develops eight chip select lines, four even and four odd chip select
lines. Each chip select line selects one row of 16K word
RAM
(note that a chip select line in Figure
2-9 goes to every other chip in each row. The effect is for a five chip row instead of ten chips, and
the chip select goes to either the odd numbered chips or the even numbered chips.) Each word is
still 32 data bits and 7 check bits, and the specific word that is addressed is selected within the block,
by the X and Y address bits.
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