Setting Example Of The Chip Select Area - Fujitsu FR60 Hardware Manual

4.3

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 64K bytes, anywhere
in the 4 Gbytes space using ASR0 to ASR7 (Area Select Registers) and ACR0 to ACR7 (Area
Configuration Registers). When bus access is made to an area specified by these registers, the
corresponding chip select signals (CS0 to CS7) are activated ("L" output) during the access
cycle.
❍ Example of setting ASRs and ASZ3 to ASZ0
• ASR1=0003
0003FFFF
• ASR2=0FFC
0FFFFFFF
• ASR3=0011
001FFFFF
Since at this point 1M bytes is set for bits ASZ3 to ASZ0 of the ACR, the unit for boundaries 1
Mbyte and bit19 to bit16 of ASR3 are ignored. Before there is any writing to ACR0 after a reset,
00000000
Set the chip select areas so that there is no overlap.
Figure 4.3-1 shows an example of setting the chip select area.
(Initial value)
00000000
FFFFFFFF
ACR1 ASZ3 to ASZ0=0000
H
.
H
ACR2 ASZ3 to ASZ0=0010
H
.
H
ACR3 ASZ3 to ASZ0=0100
H
.
H
to FFFFFFFF is assigned to chip select area 0.
H H
Figure 4.3-1 Example of Setting the Chip Select Area
H
Area 0
H
CHAPTER 4 EXTERNAL BUS INTERFACE
: 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
(Example)
00000000
H
00030000
H
Area 1
0003FFFF
H
00100000
H
Area 3
001FFFFF
H
0FFC0000
H
Area 2
0FFFFFFF
H
FFFFFFFF
H
to
H
to
H
to
H
64 Kbytes
1 Mbytes
256 Kbytes
181