Intel 386

14-9
CHIP-SELECT UNIT
Example 4
This example establishes two 16-Kbyte address blocks starting at 0E08000H and 0E28000H (16-
Kbyte boundaries).
Because the least-significant 0 in the channel mask is in bit position 4, this channel’s active ad-
dress block size is 2
4
= 16 Kbytes. Because there is one 1 to the left of the right-most 0 in the
channel mask, the address block is repeated 2
1
= 2 times. Unlike the other examples, there is a 1
in the channel mask where there is a 1 in the channel address. For this reason, the channel address
is not the starting address of the lowest active address block. In this example, each active 16-
Kbyte address block is followed by an inactive 16-Kbyte address block and each block starts at
a 16-Kbyte address boundary.
15 1
15-bit Channel Address 0 0 1 1 1 0 0 0 1 0 1 0 0 0 0
15-bit Channel Mask 0 0 0 0 0 0 0 0 1 0 0 0 1 1 1
25 0
Channel Active Address 0 0 1 1 1 0 0 0 X 0 1 0 X X X X X X X X X X X X X X
Maximum
Memory Address
0E2C000H
Active
0E2BFFFH
0E28000H
0E0C000H
Active
0E0BFFFH
0E08000H