4-14
Registers
vendor-specific. Please see
for additional information on
downloading a value for this register.
Registers: 0x30–0x33
Expansion ROM Base Address (ERBA)
Read/Write
This four-byte register handles the base address and size information for
the expansion ROM.
ERBA
Expansion ROM Base Address
[31:11]
Bits [31:11] correspond to the upper 21 bits of the
expansion ROM base address. The host system detects
the size of the external memory by first writing the
Expansion ROM Base Address (ERBA)
register with all
ones and then reading back the register. The
LSI53C1000 responds with zeros in all don’t care
locations. The least significant one (1) that remains
represents the binary version of the external memory
size. For example, to indicate an external memory size of
32 Kbytes, this register, when written with ones and read
back, returns ones in the upper 17 bits.
The size of the external memory is set through MAD[3:1].
Please see
Section 3.9, “MAD Bus Programming,”
for the
possible size encodings available.
R
Reserved
[10:1]
EREN
Expansion ROM Enable
0
The expansion ROM Enable bit, bit 0, is the only bit
defined in this register. This bit is used to control whether
or not the device accepts accesses to its expansion
ROM. When the bit is set, address decoding is enabled,
and a device is used with or without an expansion ROM
depending on the system configuration.
Note:
To access the external memory interface, also set the
Memory Space bit in the
register.
31
11 10
1
0
ERBA
R
EREN
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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...