參數(shù)資料
型號: DSP1629
英文描述: TVS 400W 64V UNIDIRECT SMA
中文描述: DSP1629數(shù)字信號處理器
文件頁數(shù): 44/126頁
文件大小: 1993K
代理商: DSP1629
Data Sheet
March 2000
DSP1629 Digital Signal Processor
44
Lucent Technologies Inc.
5 Software Architecture
(continued)
Cache Instructions
Cache instructions require one word of program memory. The do instruction executes in one instruction cycle, and
the redo instruction executes in two instruction cycles. (If PC points to external memory, add programmed wait-
states.) Control instructions and long immediate values cannot be stored inside the cache. The instruction formats
are as follows:
I
do K {
I
instr1
I
instr2
I
.
I
.
I
.
I
instrN
I
}
I
redo K
The assembly-language statement,
do cloop
(or
redo cloop
), is used to specify that the number of iterations is to be taken from the
cloop
register. K is encoded as 0 in the instruction encoding to select
cloop
.
When the cache is used to execute a block of instructions, the cycle timings of the instructions are as follows:
1. In the first pass, the instructions are fetched from program memory and the cycle times are the normal out-of-
cache values, except for the last instruction in the block of N instructions. This instruction executes in two cycles.
2. During pass two through pass K – 1, each instruction is fetched from cache and the in-cache timings apply.
3. During the last (Kth) pass, the block of instructions is fetched from cache and the in-cache timings apply, except
that the timing of the last instruction is the same as if it were out-of-cache.
4. If any of the instructions access external memory, programmed wait-states must be added to the cycle counts.
The redo instruction treats the instructions currently in the cache memory as another loop to be executed K times.
Using the redo instruction, instructions are reexecuted from the cache without reloading the cache.
The number of iterations, K, for a
do
or
redo
can be set at run time by first moving the number of iterations into the
cloop
register (7 bits unsigned), and then issuing the
do cloop
or
redo cloop
. At the completion of the loop, the
value of
cloop
is decremented to 0; hence,
cloop
needs to be written before each
do cloop
or
redo cloop
.
Table 20. Replacement Table for Cache Instructions
Replace
Instruction
Encoding
K
cloop
Meaning
Number of times the instructions are to be executed taken from bits 0—6 of the cloop
register.
Number of times the instructions to be executed is encoded in the instruction.
1 to 15 instructions can be included.
1 to 127
1 to 15
N
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