ADSP-2184L(Rev0) Ver la hoja de datos (PDF) - Analog Devices
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ADSP-2184L Datasheet PDF : 31 Pages
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ADSP-2184L
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-2184L 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-2184L
initiates a BDMA boot sequence when RESET is released.
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.
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 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-2184L. The only memory address bit provided by the
processor is A0.
IDMA Booting
The ADSP-2184L can also boot programs through its Internal
DMA port. If Mode C = 1, Mode B = 0, and Mode A = 1, the
ADSP-2184L 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-2184L 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-2184L 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.
If Go Mode is enabled, the ADSP-2184L will not halt program
execution until it encounters an instruction that requires an
external memory access.
If the ADSP-2184L is performing an external memory access
when the external device asserts the BR signal, it will not three-
state the memory interfaces or assert the BG signal until the
processor cycle after the access completes. The instruction does
not need to be completed when the bus is granted. If a single
instruction requires two external memory accesses, the bus will
be granted between the two accesses.
When the BR signal is released, the processor releases the BG
signal, reenables the output drivers and continues program
execution from the point at which it stopped.
The bus request feature operates at all times, including when
the processor is booting and when RESET is active.
The BGH pin is asserted when the ADSP-2184L is ready to
execute an instruction but is stopped because the external bus is
already granted to another device. The other device can release
the bus by deasserting bus request. Once the bus is released, the
ADSP-2184L deasserts BG and BGH and executes the external
memory access.
–10–
REV. 0
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