lf3321qc9 LOGIC Devices Incorporated, lf3321qc9 Datasheet - Page 20

• Manufacturer Part Number: lf3321qc9
• Description: Horizontal Digital Image Filter
• Manufacturer: LOGIC Devices Incorporated

DEVICES INCORPORATED
Accumulator
Access Mode
LOGIC Devices Incorporated
Operating Modes
Accumulator access allows the user to accumulate the Filter A output with the Filter B output. Therefore,
this mode is only valid when the device has been configured for dual filter operation. To configure the device
for this mode, bit 1 and bit 5 must be set to 1; bit 5 is the corresponding accumulator access bit (Table
7). Writing 022H to Configuration Register 5 configures the device to accumulate the Filter A output with
the Filter B output. All remaining Configuration Registers, 0 through 4 inclusive, will depend on specific
application requirements (see Tables 2 through 4). In this mode of operation, the accumulated output is
realized at DOUT15-0. The output data at ROUT15-0/COUT15-0 is the Filter B output that is normally
expected; however, the accumulated output data (DOUT15-0) will be delayed by one clock cycle, compared
to the Filter B output data.
This type of operation is useful when two filtered data streams (i.e. I+jQ) need to be accumulated. Such
is the requirement to satisfy the equation, y(t) = cos(vt)+jsin(vt). The complex data can be streamed and
filtered using a respective ‘I’ filter and ‘Q’ filter. To convert the complex result into a real result, as seen at the
LF3321 output, two multiplies and one accumulation is required. The cosine and sine functions are realized
through the coefficient sets; consequently, multiplied by the corresponding ‘I’ and ‘Q’ data streams. To satisfy
the remainder of the equation, Filter A and Filter B must be accumulated.
As previously stated, this mode of operation is only valid with the dual filter mode configuration. All modes of
operation, that are valid in the dual filter mode, are valid with the accumulator access mode. For additional
considerations, refer to the corresponding mode of operation section.
Figure 21. Double Wide Data Coefficient Mode
Figure 22. Accumulator Access Mode
DIN
RIN
11-0
11-0
12
12
DIN
11-0
12
20
REGISTERS
DOUT
CIRCUIT
16
REGISTERS
FILTER
R.S.L.
DOUT
CIRCUIT
16
FILTER
R.S.L.
I/D
A
I/D
A
15-0
15-0
SCALE
ROUT
REGISTERS
CIRCUIT
FILTER
16
3-0
Horizontal Digital Image Filter
R.S.L.
I/D
/ COUT
B
11-0
REGISTERS
FILTER
I/D
B
Improved Performance
12
RIN
Video Imaging Products
11-0
Feb 5, 2003 LDS.3321-A
LF3321