PDSP16256/A
Programmable FIR Filter
DS3709
ISSUE 7.1
June 1999
Features
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Ordering Information
Commercial (0
°
C to
170
°
C)
PDSP16256A/C0/AC 25MHz, PGA package
Industrial (240
°
C to
185
°
C)
PDSP16256 B0/AC 20MHz, PGA package
PDSP16256 B0/GC 20MHz, QFP package
Military (255
°
C to
1125
°
C)
PDSP16256 MC/AC1R 20MHz, MIL-STD-883*
(latest revision), PGA package
PDSP16256 MC/GC1R 20MHz, MIL-STD-883*
(latest revision), QFP package
*See notes following Electrical Characteristics for further
information on MIL-STD-883 screening
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Sixteen MACs in a Single Device
Basic Mode is 16-Tap Filter at up to 25MHz
Sample Rates
Programmable to give up to 128 Taps with
Sampling Rates Proportionally Reducing to
3·125MHz
16-bit Data and 32-bit Accumulators
Can be configured as One Long Filter or Two
Half-Length Filters
Decimate-by-two Option will Double the Filter
Length
Coefficients supplied from Host System or local
EPROM
Applications
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Associated Products
PDSP16350
I/Q Splitter/NCO
PDSP16510A
FFT Processor
High Performance Digital Filters
Description
The PDSP16256 contains sixteen multiplier -
accumulators, which can be multi cycled to provide
from 16 to 128 stages of digital filtering. Input data
and coefficients are both represented by 16-bit
two’s complement numbers with coefficients
converted internally to 12 bits and the results being
accumulated up to 32 bits.
In 16-tap mode the device samples data at the
system clock rate of up to 25MHz. If a lower sample
rate is acceptable then the number of stages can be
increased in powers of two up to a maximum of 128.
Each time the number of stages is doubled, the
sample clock rate must be halved with respect to the
system clock. With 128 stages the sample clock is
therefore one eighth of the system clock.
In all speed modes devices can be cascaded to
provide filters of any length, only limited by the
possibility of accumulator overflow. The 32-bit
results are passed between cascaded devices
without any intermediate scaling and subsequent
loss of precision.
The device can be configured as either one long
filter or two separate filters with half the number of
taps in each. Both networks can have independent
inputs and outputs.
Both single and cascaded devices can be operated
in decimate-by-two mode. The output rate is then
half the input rate, but twice the number of stages
are possible at a given sample rate. A single device
with a 20MHz clock would then, for example,
provide a 128-stage low pass filter, with a 5MHz
input rate and 2·5MHz output rate.
Coefficients are stored internally and can be down
loaded from a host system or an EPROM. The latter
requires no additional support, and is used in stand
alone applications. A full set of coefficients is then
automatically loaded at power on, or at the request
of the system. A single EPROM can be used to
provide coefficients for up to 16 devices.
PDSP16256/A
EPROM
ADDR DATA
CHANGE
COEFF
POWER-ON
RESET
RES
INPUT
DATA
PDSP
16256
EPROM
SCLK
GND
OUTPUT
DATA
Figure. 1 A dual filter application
EPROM
ADDR DATA
CHANGE
COEFF
POWER-ON
RESET
RES
COEFFICIENTS
PDSP
16256
ANALOG
INPUT
ADC
EPROM
CLKOP
SCLK
GND
OUTPUT
DATA
Figure. 2 Typical system application
2
PDSP16256/A
Signal
DA15:0
DB15:0
X31:0
16-bit data input bus to Network A.
Delayed data output bus in the single filter mode. Connected to the data input bus of the next device in a
cascaded chain. Input to Network B in the dual filter modes.
Expansion input bus in the single filter mode. Connected to the previous filter output in a cascaded chain.
The inputs are not used on a single device system or on the Termination device in a cascaded chain. The
X bus provides the output from Network B in both dual modes.
In single filter mode this bus holds the main device output. In dual mode it holds the output from Network A.
Filter enable. The first high present on an SCLK rising edge defines the first data sample. The control register
and coefficient memory must be configured befor FEN is enabled.The signal must stay active whilst valid
data is being received and must be low if FRUN is high.
Delayed filter enable. This output is connected to the Filter Enable input of the next device in a cascaded
chain when moving towards the termination device and with multiple stand-alone EPROM-loaded
configurations. It is used to coordinate the control logic within each device.
Selects either the upper or lower set of coefficients for Bank Swap. A low selects the lower bank, a high the
upper bank.
In EPROM load mode, when high this signal allows continuous filter operations to occur without the need for
the initial FEN edge. If the device is not a single, interface or master device then this pin must be tied low.
A low on this signal on the SCLK rising edge will clear all the internal accumulators.
DCLR
need only remain
low for a single cycle, signal BUSY will indicate when the internal clearing is complete. After a clear the
device must be re-synchronised to the data stream using FEN. It is recommended that FEN is taken low
at the same time as clear. FEN may then be taken high to synchronise the data stream once BUSY has
returned low.
C15:0
A7:0
CCS
WEN
CS
BYTE
EPROM
Description
F31:0
FEN
DFEN
SWAP
FRUN
DCLR
16-bit coefficient input bus. In the Byte mode of operation, C15:8 have alternative uses as explained in the
text.
Coefficient address bus. In the EPROM mode A7:0 are address outputs for an EPROM. In the remote host
mode they are inputs from the host. A7 is not used when coefficients are loaded as 16-bit words.
This pin is similar in operation to A7:0 and provides a higher order address bit. When low the coefficients
are loaded, when high the control register is loaded.
In the remote mode this pin is an input which when low enables the load operation. In the EPROM mode
it is an output which provides the write enable for other slave devices.
This pin is always an input and must also be low for the internal write operation to occur.
When this pin is tied low, coefficients are loaded as two 8-bit bytes. When the pin is high they are loaded
as 16-bit words. In the EPROM mode this pin is ignored.
When this pin is tied low coefficients are loaded as bytes from an external EPROM. The device outputs an
address on A7:0. When the pin is high coefficients must be loaded from a remote master. They can then
be transferred individually rather than as a complete set.
The main system clock; all operations are synchronous with this clock. The clock rate must be either 1, 2,
4, or 8 times the required data sampling rate. The factor used depends on the required filter length.
This output, when used to enable SCLK, can provide a data sampling clock. It has the effect of dividing the
SCLK rate by 1, 2, 4 or 8 depending on the filter mode selected.
Tri-state enable for the F bus. When high the outputs will be high impedance.
OEN
is registered onto the
device and does not therefore take effect until the first SCLK rising edge
SCLK
CLKOP
OEN
BUSY
RES
A high on this signal indicates that the device is completing internal operations and is not yet able to accept
new data. The signal is used during automatic EPROM loading, reset and accumulator clearing.
When this pin is low the control logic and accumulators are reset. In the EPROM mode it will initiate a load
sequence when it goes high.
NOTES
1. Unused buses (e.g. X31:0 when the device is configured in single or termination mode) can be set to any value. They should however be
maintained at a valid logic level to avoid an increase in power consumption.
2. To ensure correct input voltage thresholds are maintained all the V
DD
and GND pins must be connected to adequate power and ground planes.
Table 1 Pin descriptions
3
PDSP16256/A
R
P
N
M
L
K
J
H
EXTRA PIN D4,
CONNECTED TO D3
G
F
E
D
C
B
A
AC144
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Fig. 3a Pin connections for 144 pin PGA package (bottom view)
PIN 1 INDEX
PIN 1
PIN 172
GC172
Fig. 3b Pin connections for 172 pin QFP (top view)
Figure. 3 Pin connection diagrams (not to scale). See Table 1 for signal descriptions and Table 2 for
pinouts.
4
PDSP16256/A
GG
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
AC
A15
B15
D13
C14
G15
C15
D14
J15
E13
D15
E14
E15
F13
F14
F15
-
G14
G13
H14
-
H15
H13
J14
K15
-
J13
K14
-
L15
K13
L14
M15
L13
M14
N15
-
N14
M13
P15
-
P14
N13
R15
Signal
F0
F1
F2
F3
V
DD
F4
F5
GND
F6
F7
F8
F9
F10
F11
F12
GND
F13
F14
F15
V
DD
F16
F17
F18
F19
V
DD
F20
F21
GND
F22
F23
F24
F25
F26
F27
F28
GND
F29
F30
F31
V
DD
FEN
DFEN
DCLR
GG
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
AC
R14
-
N12
P13
-
R13
P12
N11
R12
P11
R11
R9
N10
P10
R10
P9
R7
N9
P8
R8
N8
P7
R6
-
N7
P6
R5
N6
P5
R4
-
N5
P4
R3
P3
N4
-
R2
P2
N3
-
-
R1
Signal
SWAP
GND
OEN
GG
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
AC
P1
-
-
N2
N1
M2
-
L3
M1
M3
-
L2
L1
K3
K2
K1
J2
J3
G1
H2
H1
J1
H3
G2
F1
G3
-
F2
E1
F3
E2
D1
-
E3
D2
C1
C2
D3
B1
B2
-
C3
-
Signal
C15
GND
GND
WEN
GG
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
AC
-
A1
A2
-
C4
B3
A3
B4
C5
A4
-
B5
A5
A7
C6
B6
A6
B7
C7
B8
A9
A8
C8
B9
A10
C9
B10
A11
C10
-
B11
A12
C11
-
B12
A13
B13
C12
A14
-
B14
-
C13
Signal
GND
BUSY
X0
V
DD
X1
X2
X3
X4
X5
X6
GND
X7
X8
V
DD
X9
X10
X11
X12
X13
X14
GND
X15
X16
X17
X18
X19
X20
X21
X22
GND
X23
X24
X25
V
DD
X26
X27
X28
X29
X30
GND
X31
V
DD
FRUN
CLKOP
V
DD
DA0
DA1
DA2
DA3
DA4
DA5
GND
DA6
DA7
DA8
DA9
V
DD
DA10
DA11
DA12
DA13
DA14
DA15
GND
C0
C1
C2
C3
C4
C5
V
DD
C6
C7
C8
C9
C10
GND
C11
C12
C13
V
DD
GND
C14
CCS
CS
V
DD
RES
SLCK
GND
V
DD
BYTE
EPROM
A0
A1
A2
A3
A4
V
DD
A5
A6
GND
A7
DB0
DB1
DB2
GND
DB3
DB4
DB5
DB6
DB7
V
DD
DB8
DB9
DB10
DB11
DB12
DB13
DB14
GND
DB15
V
DD
NOTE. All GND and V
DD
pins must be used
Table 2 Pin connections for AC144 and GC172 packages
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