User’s Manual
C166S V1 SubSystem
The External Bus Interface
User’s Manual
8-28
V 1.6, 2001-08
Definition of Address Areas
The four register pairs BUSCON4/ADDRSEL4-BUSCON1/ADDRSEL1 allow 4 address
areas to be defined within the address space of the C166S. 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 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 (marked “R”) that are not implicitly used for addresses inside the
window are used. The lower bits of the start address (marked “x”) are disregarded.
Address Window Arbitration
The address windows that can be defined within the C166S’s address space may partly
overlap each other. Thus small areas may be cut out of bigger windows, for example, in
order to utilize external resources effectively, especially within segment 0.
For each access, the EBC compares the current address with all address-select
registers (programmable ADDRSELx and hardwired/programmable XADRSx
1)
). This
comparison is done in three levels. The XADRSx registers have the highest priority
(priority I). The ADDRSEL registers have the second highest priority (priority II). If there
is no match with any XADRSx or ADDRSELx register, the access to the external bus
uses register BUSCON0 (priority III).
Table 8-6
Address Window Definition
Bit field RGSZ Resulting Window Size
Relevant Bits (R) of Start Addr. (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
1)
The XADR registers are the control registers of the internal XBUS interface (see
Section 8.7
).
Содержание C166S V1 SubSystem
Страница 10: ...User s Manual C166S V1 SubSystem User s Manual I 6 V 1 6 2001 08...
Страница 16: ...User s Manual C166S V1 SubSystem Introduction User s Manual 1 6 V 1 6 2001 08...
Страница 126: ...User s Manual C166S V1 SubSystem Central Processing Unit User s Manual 3 96 V 1 6 2001 08...
Страница 178: ...User s Manual C166S V1 SubSystem Memory Organization User s Manual 4 52 V 1 6 2001 08...
Страница 206: ...User s Manual C166S V1 SubSystem Instruction Set User s Manual 5 28 V 1 6 2001 08...
Страница 306: ...User s Manual C166S V1 SubSystem Detailed Instruction Set User s Manual 6 100 V 1 6 2001 08...
Страница 362: ...User s Manual C166S V1 SubSystem The External Bus Interface User s Manual 8 40 V 1 6 2001 08...
Страница 452: ...User s Manual C166S V1 SubSystem General Purpose Timer Unit User s Manual 12 44 V 1 6 2001 08...
Страница 454: ...User s Manual C166S V1 SubSystem Instruction Index User s Manual 13 2 V 1 6 2001 08...
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