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Special Filter Instructions
4-67
Assembly Language Instructions
Figure 4–6. Setup and Execution of MSP50P614/MSP50C614 Filter Instructions,
N+1 Taps
Accumulators
0–15
th
bits of y
16–31
st
bits of y
32–47
th
bits of y
AC
r
AC
r
+1
AC
r
+2
y[k] = Σ
m
=0..N
h[
m
]
x
[k–
m
]
+
MultiplierPH MR
Past N samples,
x
[
k
]
Coefficients, h[
k
]
k = 0..N
Data memory
(FIR/COR)
Program memory (FIRK/CORK)
sample_buf
coeff_array
AC
r
+1AC
r
+2 AC
r
y =
For COR/CORK
AC
r
AC
r
+1y =
For FIR/FIRK
TAG=1 for 2
nd
to last sample for
Circular buffer operation
+
Accumulators Pointer
Point to accumulator, ACrA
n
= AC
n
Circular buffer operation only
Circular buffer length, –2NR5
sample_buf
address
Rx
even
{R0,R2,R4,R6}
coeff_array
address
DP
coeff_array
address
Rx
even
+1
{R1,R3,R5,R7}
FIR/COR only
FIRK/CORK only
†
The value of y is stored in AC
r
and AC
r
+1 for FIR instruction (32 bit accumulation). COR instruction uses 48 bit accumulation
and includes accumulator AC
r
+2.
coeff_array
Coefficients, h[
k
]
k = 0..N