ST10R272L - EXTERNAL BUS INTERFACE
169/320
9.4.2
Defining address areas
The four register pairs BUSCON4/AD-DRSEL4...BUSCON1/ADDRSEL1 are used to define
4 separate address areas within the address space of the ST10R272L. Within each of these
address areas external accesses can be controlled by one of the four different bus modes,
independent of each other and of the bus mode specified in register BUSCON0. Each
ADDRSELx register in a way cuts out an address window, within which the parameters in
register BUSCONx are used to control external accesses. The range start address of such a
window, defines the upper address bits, which are not used within the address window of the
specified size (see table below). For a given window size only those upper address bits of
the start address are used (marked “R”), which are not implicitly used for addresses inside
the window. The lower bits of the start address (marked “x”) are disregarded.
9.4.3
Prioritizing address areas
A prioritizing scheme is used to allow overlapping of address areas. The ADDRSELs
registers are split into two groups:
•
The first group with ADDRSEL1 and ADDRSEL2, gives to ADDRSEL2 a higher priority
than ADDRSEL1. Thus, an overlapping among address areas defined via registers
ADDRSEL1 and 2 is allowed.
Bit field
RGSZ
Resulting
Window
Size
Relevant Bits (R) of Start Address (A23...A12)
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0
1 0 0 1
1 0 1 0
1 0 1 1
1 1 x x
4 KByte
8 KByte
16 KByte
32 KByte
64 KByte
128 KByte
256 KByte
512 KByte
1 MByte
2 MByte
4 MByte
8 MByte
Reserved.
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
X
R
R
R
R
R
R
R
R
R
R
X
X
R
R
R
R
R
R
R
R
R
X
X
X
R
R
R
R
R
R
R
R
X
X
X
X
R
R
R
R
R
R
R
X
X
X
X
X
R
R
R
R
R
R
X
X
X
X
X
X
R
R
R
R
R
X
X
X
X
X
X
X
R
R
R
R
X
X
X
X
X
X
X
X
R
R
R
X
X
X
X
X
X
X
X
X
R
R
X
X
X
X
X
X
X
X
X
X
R
X
X
X
X
X
X
X
X
X
X
X
Table 29 Address area definition