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4.4 Area Select Register (ASR) and Area Mask Register (AMR)
The area select registers (ASR1 to ASR5) and area m ask registers (AMR1 to AMR5) specify the
range of address space for chip select areas 1 to 5.
ASR1 to ASR5 specify the upper 16 bits (A31 to A16) of eac h address, and AMR1 to AMR5
mask the corresponding address bits. Each bit of AM R1 to AMR5 assumes "care" by "0" and
"dont care" by "1".
When the value set in the ASR is "0", "care" indicates the address space as "0". When it is "1",
"care" indicates the address space as "1".
"Dont care" indicates the address space for both "0" and "1", that is, i rrespective of the val ue
set in the ASR.
The following is an example of specifying each chip se lect are a by combin ation of th e ASR and
AMR:
(Example 1)
are set, the AMR1 bits corresponding to the ASR bits that are set to "1" are "0", and the ad dres s
space of area 1 becomes 64 kilobytes, as shown below.
(Example 2)
are set, the ASR2 bits corresponding to the AMR2 bits that ar e set to "0" are "1" and "0" to
indicate "care", while the ASR2 bits corresponding to the AMR2 bits that are set to "1" are "0" or
"1" to indicate "dont care". Therefore, the address space of area 2 be comes 256 kilobyt es, as
shown below.
The address space of each of areas 1 to 5 can be optionally located in at least 64 kilobytes in a
4 gigabyte space, using ASR1 to ASR5 and AMR1 to AMR5. When the area specified by these
registers is accessed via the bus, the corresponding chip selec t pins (CS0X to CS5X) are
handled as L outputs.
Area 0 is allocated to a space other than the areas specified by ASR1 to ASR5 and AM R1 to
AMR5. When these registers are reset, an area other than 00010000H and 0005FFFFH is
allocated by the initial values of ASR1 to ASR5 and AMR1 t o AMR5.
<Note>
Set chip select areas such that overlapping does not oc cur.
When ASR1 = 00000000 00000 011B
and A MR1 = 00000000 00000000B
00000000 000000 11 00000000 00000000B(00030000H)
to
00000000 000000 11 11111111 11111111B(0003FFFFH)
When ASR2 = 00001111 11111111B
and AMR2 = 00000000 00000011B
00001111 11111100 00000000 00000000B(0FFC0000H)
to
00001111 11111111 11111111 11111111B(0FFFFFFFH)