
ADSP-2185
–3–
REV. 0
T he internal result (R) bus connects the computational units so
the output of any unit may be the input of any unit on the next
cycle.
A powerful program sequencer and two dedicated data address
generators ensure efficient delivery of operands to these compu-
tational units. T he sequencer supports conditional jumps, sub-
routine calls and returns in a single cycle. With internal loop
counters and loop stacks, the ADSP-2185 executes looped code
with zero overhead; no explicit jump instructions are required to
maintain loops.
T wo data address generators (DAGs) provide addresses for
simultaneous dual operand fetches from data memory and pro-
gram memory. Each DAG maintains and updates four address
pointers. Whenever the pointer is used to access data (indirect
addressing), it is post-modified by the value of one of four pos-
sible modify registers. A length value may be associated with
each pointer to implement automatic modulo addressing for
circular buffers.
Efficient data transfer is achieved with the use of five internal
buses:
Program Memory Address (PMA) Bus
Program Memory Data (PMD) Bus
Data Memory Address (DMA) Bus
Data Memory Data (DMD) Bus
Result (R) Bus
T he two address buses (PMA and DMA) share a single external
address bus, allowing memory to be expanded off-chip, and the
two data buses (PMD and DMD) share a single external data
bus. Byte memory space and I/O memory space also share the
external buses.
Program memory can store both instructions and data, permit-
ting the ADSP-2185 to fetch two operands in a single cycle, one
from program memory and one from data memory. T he ADSP-
2185 can fetch an operand from program memory and the next
instruction in the same cycle.
When configured in host mode, the ADSP-2185 has a 16-bit
Internal DMA port (IDMA port) for connection to external
systems. T he IDMA port is made up of 16 data/address pins
and five control pins. T he IDMA port provides transparent,
direct access to the DSPs on-chip program and data RAM.
An interface to low cost byte-wide memory is provided by the
Byte DMA port (BDMA port). T he BDMA port is bidirectional
and can directly address up to four megabytes of external RAM
or ROM for off-chip storage of program overlays or data tables.
T he byte memory and I/O memory space interface supports
slow memories and I/O memory-mapped peripherals with
programmable wait state generation. External devices can
gain control of external buses with bus request/grant signals
(
BR
,
BGH
and
BG
). One execution mode (Go Mode) allows
the ADSP-2185 to continue running from on-chip memory.
Normal execution mode requires the processor to halt while
buses are granted.
T he ADSP-2185 can respond to eleven interrupts. T here can be
up to six external interrupts (one edge-sensitive, two level-sensitive
and three configurable) and seven internal interrupts generated
by the timer, the serial ports (SPORT s), the Byte DMA port
and the power-down circuitry. T here is also a master
RESET
signal. T he two serial ports provide a complete synchronous
serial interface with optional companding in hardware and a
wide variety of framed or frameless data transmit and receive
modes of operation.
Each port can generate an internal programmable serial clock or
accept an external serial clock.
T he ADSP-2185 provides up to 13 general-purpose flag pins.
T he data input and output pins on SPORT 1 can be alternatively
configured as an input flag and an output flag. In addition,
eight flags are programmable as inputs or outputs, and three
flags are always outputs.
A programmable interval timer generates periodic interrupts. A
16-bit count register (T COUNT ) decrements every
n
processor
cycle, where
n
is a scaling value stored in an 8-bit register
(T SCALE). When the value of the count register reaches zero,
an interrupt is generated and the count register is reloaded from
a 16-bit period register (T PERIOD).
Serial Ports
T he ADSP-2185 incorporates two complete synchronous serial
ports (SPORT 0 and SPORT 1) for serial communications and
multiprocessor communication.
Here is a brief list of the capabilities of the ADSP-2185 SPORT s.
For additional information on Serial Ports, refer to the
ADSP-
2100 Family User’s Manual
.
SPORT s are bidirectional and have a separate, double-buff-
ered transmit and receive section.
SPORT s can use an external serial clock or generate their own
serial clock internally.
SPORT s have independent framing for the receive and trans-
mit sections. Sections run in a frameless mode or with frame
synchronization signals internally or externally generated.
Frame sync signals are active high or inverted, with either of
two pulse widths and timings.
SPORT s support serial data word lengths from 3 to 16 bits
and provide optional A-law and
μ
-law companding according
to CCIT T recommendation G.711.
SPORT receive and transmit sections can generate unique
interrupts on completing a data word transfer.
SPORT s can receive and transmit an entire circular buffer of
data with only one overhead cycle per data word. An interrupt
is generated after a data buffer transfer.
SPORT 0 has a multichannel interface to selectively receive
and transmit a 24 or 32 word, time-division multiplexed,
serial bitstream.
SPORT 1 can be configured to have two external interrupts
(
IRQ0
and
IRQ1
) and the Flag In and Flag Out signals. T he
internally generated serial clock may still be used in this con-
figuration.
PIN DE SCRIPT IONS
T he ADSP-2185 will be available in a 100-lead T QFP package.
In order to maintain maximum functionality and reduce pack-
age size and pin count, some serial port, programmable flag,
interrupt and external bus pins have dual, multiplexed function-
ality. T he external bus pins are configured during RESET only,
while serial port pins are software configurable during program
execution. Flag and interrupt functionality is retained concur-
rently on multiplexed pins. In cases where pin functionality is
reconfigurable, the default state is shown in plain text; alternate
functionality is shown in italics.