TLC32047C Datasheet, PDF (34/61 Pages) Texas Instruments – Wide-Band Analog Interface Circuit

Table 2–6. (sin x)/x Correction Table for f_s = 8000 Hz and f_s = 9600 Hz
ROLL-OFF ERROR (dB) ROLL-OFF ERROR (dB)
f (Hz)
fs = 8000 Hz
p1 = – 0.14813
fs = 9600 Hz
p1 = – 0.1307
p2 = 0.9888
p2 = 0.9951
300
– 0.099
– 0.043
600
– 0.089
– 0.043
900
– 0.054
0
1200
– 0.002
0
1500
0.041
0
1800
0.079
0.043
2100
0.100
0.043
2400
0.091
0.043
2700
– 0.043
0
3000
– 0.102
– 0.043
2.29 TMS320 Software Requirements
The digital correction filter equation can be written in state variable form as follows:
y_(i+1) = y_(i) × k1 + u_(i+1) × k2
where
k1 = p1
k2 = (1 – p1)p2
y(i) is the filter state
u(i+1)
The coefficients k1 and k2 must be represented as 16-bit integers. The SACH instruction (with the proper
shift) yields the correct result. With the assumption that the TMS320 processor page pointer and memory
configuration are properly initialized, the equation can be executed in seven instructions or seven cycles
with the following program:
ZAC
LT K2
MPY U
LTA K1
MPY Y
APAC
SACH (dma), (shift)
2–16