I/O Instructions
5-19
generate the address of the required data. Both positive
and negative offsets are allowed. A subsequent fetch
from that address brings the data values into the chip.
SCRIPTS can directly execute operating system I/O data
structures, saving time at the beginning of an I/O
operation. The I/O data structure can begin on any Dword
boundary and may cross system segment boundaries.
There are two restrictions on the placement of data in
system memory:
•
The I/O data structure must lie within the 8 Mbytes
above or below the base address.
•
An I/O command structure must have all four bytes
contiguous in system memory, as shown below. The
offset/period bits are ordered as in the
register. The configuration bits are ordered
as in the
register.
Use this bit only in conjunction with the Select, Reselect,
Wait Select, and Wait Reselect instructions. It is allowable
to set bits 25 and 26 individually or in combination:
Direct
Uses the device ID and physical address in the
instruction.
Table Indirect
Uses the physical jump address, but fetches data using
the table indirect method.
Config
ID
Offset/period
00
Bit 25
Bit 26
Direct
0
0
Table Indirect
0
1
Relative
1
0
Table Relative
1
1
Command
ID
Not Used
Not Used
Absolute Alternate Address
Содержание LSI53C1000
Страница 6: ...vi Preface...
Страница 16: ...xvi Contents...
Страница 28: ...1 12 Introduction...
Страница 234: ...4 124 Registers...
Страница 314: ...6 40 Specifications This page intentionally left blank...
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Страница 350: ...6 76 Specifications Figure 6 42 LSI53C1000 329 Ball Grid Array Bottom view...
Страница 352: ...6 78 Specifications...
Страница 360: ...A 8 Register Summary...
Страница 376: ...IX 12 Index...