12
FN2486.10
October 10, 2008
Operational Section
Start Configurations
The scenario to put the DDF into operational mode is: reset
the DDF by asserting the RESET input, configure the DDF
over the control bus, and apply a start signal, either by
ASTARTIN or STARTIN. Until the DDF is put in operational
mode with a start pulse, the DDF ignores all data inputs.
To use the asynchronous start, an asynchronous active low
pulse is applied to the ASTARTIN input. ASTARTIN is
internally synchronized to the sample clock, CK_IN, and
generates STARTOUT. This signal is also used internally
when the asynchronous mode is selected. It puts the DDF in
operational mode and allows the DDF to begin accepting
data. When the ASTARTIN input is being used, the STARTIN
input must be tied high to ensure proper operation.
To start the DDF synchronously, the STARTIN is asserted
with a active low pulse that has been externally
synchronized to CK_IN. Internally the DDF then uses this
start pulse to put the DDF in operate mode and start
accepting data inputs. When STARTIN is used to start the
DDF the ASTARTIN input must be tied high to prevent false
starts.
FIGURE 10. FIR OUTPUT FORMATTER
OUT_SELH
16
DATA_OUT0 -15
16 16
F_BYP
OUT_ENP
F_BYP = 1
2-16 - 2-31
F_BYP = 0
40
MUX
20 - 2-15
8
DATA_OUT16-23
8
F_BYP
OUT_ENX
F_BYP = 0
28 - 21
F_BYP = 0
MUX
2-16 - 2-23
OUT_SELH = 0
OR
F_BYP = 1
OUT_SELH = 1
INPUT DATA FORMAT
Fractional Two's Complement Input
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
-20
. 2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10 2-11 2-12 2-13 2-14 2-15
FIR COEFFICIENT FORMAT
Fractional Two's Complement Input
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
-20
. 2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10 2-11 2-12 2-13 2-14 2-15
2-16 2-17 2-18 2-19
OUTPUT DATA FORMAT
Fractional Two's Complement Output
FOR: OUT_SELH = 1, F_BYP = 0
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
-28
27
26
25
24
23
22
21
20
. 2-1 2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10 2-11 2-12 2-13 2-14 2-15
FOR: OUT_SELH = 0, F_BYP = 0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
23
22
21
20
19
18
17
16
-20
. 2-1 2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10 2-11 2-12 2-13 2-14 2-15
2-16 2-17 2-18 2-19 2-20 2-21 2-22 2-23
FOR: OUT_SELH = X, F_BYP = 1
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
2-16 2-17 2-18 2-19 2-20 2-21 2-22 2-23
2-16 2-17 2-18 2-19 2-20 2-21 2-22 2-23 2-24 2-25 2-26 2-27 2-28 2-29 2-30 2-31
FIGURE 11.
HSP43220