Setting Example Of The Chip Select Area - Fujitsu MB91460 SERIES FR60 User Manual

Chapter 31 External Bus

3.Setting Example of the Chip Select Area

3. Setting Example of the Chip Select Area
In the external bus interface, a total of eight chip select areas can be set.
This section presents an example of setting the chip select area.
■ Example of Setting the Chip Select Area
The address space of each area can be placed, in units of a minimum of 64 KB, anywhere in the 4 GB space
using ASR0-7 (Area Select Registers) and ACR0-7 (Area Configuration Registers). When bus access is made to
an area specified by these registers, the corresponding chip select signals (CS0-CS7) are activated (L output)
during the access cycle.
● Example of setting ASRs and ASZ3-0
• ASR1=0003 ACR1 ASZ3-0=0000
H
• ASR2=0FFC ACR2 ASZ3-0=0010
H
• ASR3=0011 ACR3 SZ3-0=0100
H
Since at this point 1 MB is set for bits ASZ3-0 of the ACR, the unit for boundaries 1 MB and bits 19-16 of ASR3
are ignored. Before there is any writing to ACR0 after a reset, 00000000
area 0.
Set the chip select areas so that there is no overlap.
Figure 3-1 "Example of Setting the Chip Select Area" shows an example of setting the chip select area.
(Initial value)
00000000
FFFFFFFF
542
: Chip select area 1 is assigned to 00030000
B
: Chip select area 2 is assigned to 0FFC0000
B
: Chip select area 3 is assigned to 00100000
B
Figure 3-1 Example of Setting the Chip Select Area
H
Area 0
H
-FFFFFFFF
H
(Example)
00000000
H
00030000
H
00040000
H
00100000
H
00200000
H
0FFC0000
H
0FFFFFFF
H
FFFFFFFF
H
to 0003FFFF
H H
to 10000000
H
to 00200000 .
H H
is assigned to chip select
H
Area 1 64 KB
Area 3 1 MB
Area 2 256 KB
.
.
H