Intel 386 User Manual
Page 442
14-7
CHIP-SELECT UNIT
Example 3
This example establishes four 2-Kbyte address blocks starting at 2413000H, 2433000H,
2613000H, and 2633000H.
Because the least-significant 0 in the channel’s mask is in bit position 1, this channel’s active ad-
dress block size is 2
1
= 2 Kbytes. Because there are two 1’s to the left of the right-most 0 in the
channel’s mask, the address block is repeated 2
2
= 4 times. Also, because there are no 1’s in the
channel mask where there are 1’s in the channel address, the channel address is the starting ad-
dress of the lowest active address block. In this example, each active 2-Kbyte address block in
memory is followed by an inactive 2-Kbyte address block and each active address block starts at
a 2-Kbyte boundary.
15
1
15-bit Channel Address
1 0 0 1 0 0 0 0 0 1 0 0 1 1 0
15-bit Channel Mask
0 0 0 0 1 0 0 0 1 0 0 0 0 0 0
25
0
Channel Active Address
1 0 0 1 X 0 0 0 X 1 0 0 1 1 0
X X X X X X X X X X X