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参数资料
| 型号： | STEL-1378A |
| 英文描述： | FREQUENCY SYNTHESIZER|HYBRID|DIP|64PIN|PLASTIC |
| 中文描述： | 频率合成器|混合|双酯| 64管脚|塑料 |
| 文件页数： | 7/19页 |
| 文件大小： | 284K |
| 代理商： | STEL-1378A |
7
STEL-2060C
MICROPROCESSOR INTERFACE MEMORY MAP
WRITE MODE REGISTERS
ADDR
2-0
0
1
2
3
4
5
DATA
7
COUNT
7
THR
7
DATA
6
COUNT
6
THR
6
DATA
5
COUNT
5
THR
5
DATA
4
COUNT
4
THR
4
DATA
3
COUNT
3
THR
3
DATA
2
COUNT
2
THR
2
DATA
1
COUNT
1
THR
1
DATA
0
COUNT
0
THR
0
BPER
7
BPER
15
BPER
23
BPER
6
BPER
14
BPER
22
BPER
5
BPER
13
BPER
21
BPER
4
BPER
12
BPER
20
BPER
3
BPER
11
BPER
19
BPER
2
BPER
10
BPER
18
BPER
1
BPER
9
BPER
17
BPER
0
BPER
8
BPER
16
READ MODE REGISTERS
ADDR
2-0
0
1
DATA
7
BERCT
7
BERCT
15
DATA
6
BERCT
6
BERCT
14
DATA
5
BERCT
5
BERCT
13
DATA
4
BERCT
4
BERCT
12
DATA
3
BERCT
3
BERCT
11
DATA
2
BERCT
2
BERCT
10
DATA
1
BERCT
1
BERCT
9
DATA
0
BERCT
0
BERCT
8
PUNCTURED MODE OPERATION
CONCEPT OF PUNCTURING
In punctured codes some of the symbols generated by the
convolutional encoder are deleted, or punctured, from the
transmitted sequence. For example, in a rate
1
/
2
(unpunctured) sequence, four symbols are transmitted for
every two data bits. If one symbol out of every group of
four was punctured from the sequence then only three
symbols would be transmitted for every two data bits. This
would result in a rate
2
/
3
code. The coding gain is
significantly less than that for unpunctured operation, but
this is the trade-off for the reduced bandwidth required to
transmit the information. The STEL-2060CC decoder is
designed to operate with punctured codes as well as rate
1
/
2
code. Two methods are provided for depuncturing the
symbols. The external method can be used for all rates and
patterns up to rate
7
/
8
by indicating which symbols were
punctured at the encoder (and then reinserted prior to
decoding) with the
PNCG1
and
PNCG2
signals. When one
of these signals is set high the input data at the corresponding
symbol input is ignored, and the internally generated metric
for the symbol pair (G1 and G2) assigns a zero weight to the
punctured symbol in the pair. This is done because the
Viterbi decoder has no way of knowing what the punctured
symbol should have been. The recommended puncturing
sequences for the various
(N-1)
/
N
rates of punctured
operation are shown in the tables. The portions shown in
boldface are the basic sequences, which are then repeated.
The use of the
PNCG1
and
PNCG2
signals for rate
3
/
4
is
shown in the External Puncturing timing diagrams. The
sequence for rate
3
/
4
is G1 G2 P G2 G1 P, and the punctured
symbols are marked with asterisks in the timing diagrams.
USING INTERNAL DEPUNCTURING
The internal depuncturing method supports Rates
2
/
3
,
3
/
4
and
7
/
8
using the puncturing sequences specified in the
tables, and the node sync process will automatically find the
correct places to reinsert the punctured symbols. The
puncturing sequences used for the rates supported are shown
in the tables, along with the speeds of the two input clocks,
SYMCKIN
and
DCLKIN
. The portions shown in boldface
are the basic sequences, which are then repeated. The
symbol sequence for rate
2
/
3
is shown in the Internal
Puncturing timing diagrams. The sequence is G1 G2 P G2;
only G1 symbols are punctured in this particular sequence.
The
SYMCKIN
and
DCLKIN
clocks are used to clock in the
symbols and to clock out the data bits. The speeds of these
two clocks vary according to the modes and rate in use.
When operating in the External Depuncturing modes the
DCLKIN
signal is not used and the
SYMCKIN
speed will be
equal to the data rate (D) in the parallel mode (
PARL
= 1) and
be equal to twice the data rate (2D) in the sequential mode
(
PARL
= 0). In the Internal Depuncturing modes, however,
DCLKIN
is used and the speed of
SYMCKIN
will be as
shown in the tables.
The depuncturing circuit in the STEL-2060CC takes symbols
synchronized to the SYMCKIN signal and depunctures them,
i.e., inserts dummy symbols into the signal stream at the
appropriate positions. To do this the circuit handles the
symbols as a group of up to four pairs, depending on the code
rate. This circuit operates at the SYMCKIN rate and, at this
point, the group of depunctured symbols is transferred into
another set of registers clocked with DCLKIN. There is an
internal timing requirement that the falling edge of DCLKIN
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