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

CHAPTER 4 EXTERNAL BUS INTERFACE
4.3

Setting Example of the Chip Select Area

In the external bus interface, a total of four chip select areas can be set.
The address space of each area can be placed, in units of a minimum of 64K bytes,
anywhere in the 4 GB space using ASR0 to 3 (Area Select Registers) and ACR0 to 3
(Area Configuration Registers).
When bus access is made to an area specified by these registers, the corresponding
chip select signals (CS0 to CS3) are activated (L output) during the access cycle.
■ Example of Setting ASRs and ASZ[3:0]
1. ASR1=0003
2. ASR2=0FFC
3. ASR3=0011
Since at this point 1M bytes is set for bits ASZ[3:0] of the ACR, the unit for boundaries 1M bytes and
[19:16] of ASR3 are ignored.
Before there is any writing to ACR0 after a reset, 00000000
0.
Note:
Set the chip select areas so that there is no overlap.
Figure 4.3-1 shows the chip select area.
186
ACR1 → ASZ[3:0]=0000
H
ACR2 → ASZ[3:0]=0010
H
ACR3 → ASZ[3:0]=0100
H
: Chip select area 1 is assigned to 00030000
B
0003FFFF .
H
: Chip select area 2 is assigned to 0FFC0000
B
10000000 .
H
: Chip select area 3 is assigned to 00100000
B
00200000 .
H
to FFFFFFFF
H
is assigned to chip select area
H
to
H
to
H
to
H