11DMA Ports
11 – 3
Byte memory space consists of 256 pages, each containing 16K x 8-bit wide
locations. This memory can be written and read in four different formats:
24-bit, 16-bit, 8-bit MSB alignment, and 8-bit LSB alignment.
To use byte memory for purposes other that boot loading, for example
runtime access to bulk data storage, you must know the page (BMPAGE)
that the code/data is stored on, the number of words (BWCOUNT) to read
from that page, and the word format (BTYPE) of the data. Use the following
procedure to prepare a runtime-accessible byte memory EPROM:
• Develop the data/code to be accessed at runtime
• Use the ADSP-2100 Family PROM Splitter utility to split the file into
single page (or smaller) 16K x 8-bit-wide segments
• Program these pages into your EPROM, noting the offset (page number)
of each
• Use these page numbers when doing BDMA accesses
Note: For more information on the ADSP-2100 Family Development
Software Tools, see the ADSP-2100 Family Assembler Tools & Simulator Manual
and current software release note.
When using BDMA for non-boot-loading transfers, a BDMA transfer begins when
data is written to the BWCOUNT register and a BDMA interrupt is issued when the
transfer is complete.
The following restrictions apply to BDMA transfers:
• The source or target of BDMA transfer is always internal program or data
memory. The contents of the PMOVLAY and DMOVLAY registers do not
influence BDMA source (or target selection).
• Do not access the BEAD or BIAD registers during BDMA transfers.
• Other external memory accesses (PM overlay, DM overlay, or I/O space)
take precedence over BDMA port accesses. These accesses cannot occur at
the same time because they also use the processor’s external bus.
• Do not enter powerdown mode with the BDMA port active. For
information on powerdown restrictions on BDMA port access, see the
System Interface chapter of this manual.
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