Bit Manipulation Unit (Bmu); Serial Input/Output (Sio) Units - Lucent Technologies DSP1617 Information Manual

DSP1611/17/18/27/28/29 DIGITAL SIGNAL PROCESSOR Information Manual
Hardware Architecture April 1998
2.4 External Memory Interface (EMI)
(continued)
The DSP1611/17/18/27/28/29 allows writing to external program (X) memory. Bit 11 (WEROM) and bit 14
(EXTROM) of the ioc register enable the DSP to write the external X-memory space, which is normally read-only.
If WEROM is set high, a write to or read from ERAMLO, IO, or ERAMHI memory space asserts the EROM strobe
instead of the ERAM or IO strobes, thereby allowing access to X memory. If the EXTROM bit is set in conjunction
with the WEROM bit, an entire 64K of EROM can be accessed. This feature is used by the hardware development
software, and it can be used in system applications to download a program into the external program memory
space.
If external data (Y) memory is written, the RWN signal goes low for an external cycle. The CKO output pin can pro-
vide a reference for external I/O timing. Either a free-running CKO or a wait-stated CKO can be selected. The flex-
ibility provided by the programmable options of the external memory interface allows the DSP1611/17/18/27/28/29
to interface gluelessly with a variety of commercial memory chips. A full description of the EMI is found in Chapter
6, External Memory Interface.

2.5 Bit Manipulation Unit (BMU)

The BMU adds extensions to the DSP1600 core instruction set that execute in one or two cycles for more efficient
bit operations on accumulators. The BMU contains logic for barrel shifting, normalization, and bit-field insertion or
extraction. The unit also contains a set of 36-bit alternate accumulators that can be shuffled with the working set.
Flags returned by the BMU mesh seamlessly with the conditional instructions. The BMU contains four 16-bit auxil-
iary registers ar<0—3> that contain input or output operands. The BMU is fully described in Chapter 13, Bit Manip-
ulation Unit.
The following barrel shift operations are available: arithmetic or logical shifts and left or right shifts. The shift
amount is from immediate data in the second word of the instruction, from data in ar<0—3>, or from data in an
accumulator. The normalization function is done on the accumulators by finding the exponent that is the number
of redundant sign bits of a two's complement number. The calculated exponent is placed in one of the ar
registers. The original accumulator value is shifted or normalized with respect to bit 31. In bit extraction, a contigu-
ous field of bits is moved from the source accumulator to the lowest-order bits of the destination accumulator. In bit
insertion, a contiguous field of bits in the lowest-order position of the source accumulator replaces bits at an offset
position in the destination accumulator. The other bits in the destination accumulator are filled from the corre-
sponding bits in the second source accumulator. The two alternate accumulators are used to shuffle data with one
or two working accumulators. With the shuffle instruction, data is moved from a source accumulator to an alternate
accumulator and the old data in the alternate accumulator is moved to a destination accumulator. Only one instruc-
tion cycle is required for swapping all 36 bits.

2.6 Serial Input/Output (SIO) Units

1
SIO1 and SIO2 are asynchronous, full-duplex, double-buffered channels that easily interface with other DSP16XX
devices in a multiple-processor environment. Commercially available codecs and time-division multiplex (TDM)
channels can be interfaced to the SIO with few, if any, additional components. The SIO units are fully described in
Chapter 7, Serial I/O.
An 8-bit serial protocol channel is also available in the multiprocessor mode. This feature uses the SADD pin and
saddx register to transmit an 8-bit software-definable field in addition to the address of the called processor. This
feature is useful for transmitting the source address of the data, high-level framing information, or bits for error
detection and correction.
1.XX denotes the last two digits of the device name, e.g., XX = 11 for the DSP1611.
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