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AMC Programming Model
6-18
ADSP-BF537 Blackfin Processor Hardware Reference
Byte Enables
The AMC provides byte enable pins to allow the processor to perform
efficient byte-wide arithmetic and byte-wide processing in external
memory.
In general, there are two different ways to modify a single byte within the
16-bit interface. First, it can be done by a read/modify/write sequence.
However, this is not very efficient because multiple accesses are required
(that is, it takes many cycles for reads and writes to external memory).
Another option is available where just a specific byte can be modified for a
16-bit devices using the
ABE[1:0]
pins. See
The
ABE[1:0]
pins are both low during all asynchronous reads and 16-bit
asynchronous writes. When an asynchronous write is made to the upper
byte of a 16-bit memory,
ABE1
=
0
and
ABE0
=
1
. When an asynchronous
write is made to the lower byte of a 16-bit memory,
ABE1
=
1
and
ABE0
=
0
.
AMC Programming Model
The asynchronous memory global control register (
EBIU_AMGCTL
) config-
ures global aspects of the controller. It contains bank enables and other
information as described in this section. This register should not be
Table 6-3. Byte Enables 8-Bit Write Accesses
Internal Address
IA[0]
Internal Transfer Size
byte 2
bytes
0
ABE[1] = 1
ABE[0] = 0
ABE[1] = 0
ABE[1] = 0
1
ABE[0] = 0
ABE[0] = 1
ABE[1] = 0
ABE[1] = 0
Содержание Blackfin ADSP-BF537
Страница 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...