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ADSP-2186L
–10–
REV. A
The DSP memory address is latched and then automatically incre-
mented after each IDMA transaction. An external device can
therefore access a block of sequentially addressed memory by
specifying only the starting address of the block. This increases
throughput as the address does not have to be sent for each
memory access.
IDMA Port access occurs in two phases. The first is the IDMA
Address Latch cycle. When the acknowledge is asserted, a 14-bit
address and 1-bit destination type can be driven onto the bus by
an external device. The address specifies an on-chip memory
location, the destination type specifies whether it is a DM or
PM access. The falling edge of the address latch signal latches
this value into the IDMAA register.
Once the address is stored, data can then either be read from or
written to the ADSP-2186L’s on-chip memory. Asserting the
select line (
IS
) and the appropriate read or write line (
IRD
and
IWR
respectively) signals the ADSP-2186L that a particular
transaction is required. In either case, there is a one-processor-
cycle delay for synchronization. The memory access consumes
one additional processor cycle.
Once an access has occurred, the latched address is automati-
cally incremented and another access can occur.
Through the IDMAA register, the DSP can also specify the
starting address and data format for DMA operation.
Bootstrap Loading (Booting)
The ADSP-2186L has two mechanisms to allow automatic
loading of the internal program memory after reset. The method
for booting is controlled by the Mode A, B and C configuration
bits as shown in Table VI. These four states can be compressed
into two-state bits by allowing an IDMA boot with Mode C = 1.
However, three bits are used to ensure future compatibility with
parts containing internal program memory ROM.
BDMA Booting
When the MODE pins specify BDMA booting, the ADSP-2186L
initiates a BDMA boot sequence when
RESET
is released.
The BDMA interface is set up during reset to the following de-
faults when BDMA booting is specified: the BDIR, BMPAGE,
BIAD and BEAD registers are set to 0; the BTYPE register is
set to 0 to specify program memory 24-bit words; and the
BWCOUNT register is set to 32. This causes 32 words of on-
chip program memory to be loaded from byte memory. These
32 words are used to set up the BDMA to load in the remaining
program code. The BCR bit is also set to 1, which causes program
execution to be held off until all 32 words are loaded into on-chip
program memory. Execution then begins at address 0.
The ADSP-2100 Family development software (Revision 5.02
and later) fully supports the BDMA booting feature and can
generate byte memory space compatible boot code.
The IDLE instruction can also be used to allow the processor to
hold off execution while booting continues through the BDMA
interface. For BDMA accesses while in Host Mode, the ad-
dresses to boot memory must be constructed externally to the
ADSP-2186L. The only memory address bit provided by the
processor is A0.
Table VI. Boot Summary Table
MODE C MODE B MODE A Booting Method
0
0
0
BDMA feature is used to load
the first 32 program memory
words from the byte memory
space. Program execution is
held off until all 32 words
have been loaded. Chip is
configured in Full Memory
Mode.
0
1
0
No Automatic boot opera-
tions occur. Program execu-
tion starts at external memory
location 0. Chip is config-
ured in Full Memory Mode.
BDMA can still be used but
the processor does not auto-
matically use or wait for these
operations.
1
0
0
BDMA feature is used to load
the first 32 program memory
words from the byte memory
space. Program execution is
held off until all 32 words
have been loaded. Chip is
configured in Host Mode.
Additional interface hardware
is required.
1
0
1
IDMA feature is used to load
any internal memory as de-
sired. Program execution is
held off until internal pro-
gram memory location 0 is
written to. Chip is configured
in Host Mode.
IDMA Booting
The ADSP-2186L can also boot programs through its Internal
DMA port. If Mode C = 1, Mode B = 0, and Mode A = 1, the
ADSP-2186L boots from the IDMA port. The IDMA feature
can load as much on-chip memory as desired. Program execu-
tion is held off until on-chip program memory location 0 is
written to.
Bus Request and Bus Grant
The ADSP-2186L can relinquish control of the data and ad-
dress buses to an external device. When the external device
requires access to memory, it asserts the bus request (BR) sig-
nal. If the ADSP-2186L is not performing an external memory
access, it responds to the active BR input in the following pro-
cessor cycle by:
Three-stating the data and address buses and the
PMS
,
DMS
,
BMS
,
CMS
,
IOMS
,
RD
,
WR
output drivers,
Asserting the bus grant (
BG
) signal, and
Halting program execution.