MT9300 Mitel Networks Corporation, MT9300 Datasheet - Page 16

• Manufacturer Part Number: MT9300
• Description: Multi-channel Voice Echo CANceller
• Manufacturer: Mitel Networks Corporation

MT9300
16
The Exponential Decay registers (Decay Step Number and Decay Step Size) and Flat Delay register allow the LMS adaptation
step-size (MU) to be programmed over the length of the FIR filter. A programmable MU profile allows the performance of the echo
canceller to be optimized for specific applications. For example, if the characteristic of the echo response is known to have a flat
delay of several milliseconds and a roughly exponential decay of the echo impulse response, then the MU profile can be
programmed to approximate this expected impulse response thereby improving the convergence characteristics of the Adaptive
Filter. Note that in the following register descriptions, one tap is equivalent to 125 s (64ms/512 taps).
FD
SSC
NS
Echo Canceller A, Flat Delay Register (FD)
Echo Canceller B, Flat Delay Register (FD)
Echo Canceller A, Decay Step Number Register (NS)
Echo Canceller B, Decay Step Number Register (NS)
Echo Canceller A, Decay Step Size Control Register (SSC)
Echo Canceller B, Decay Step Size Control Register (SSC)
7-0
7-0
2-0
Amplitude of MU
NS
1.0
FD
7
2
7
7
0
-16
Flat Delay: This register defines the flat delay of the MU profile, (i.e., where the MU value is 2
as FD
range of FD
0
Decay Step Size Control: This register controls the step size (SS) to be used during the exponential decay of MU. The
decay rate is defined as a decrease of MU by a factor of 2 every SS taps of the FIR filter, where SS = 4 x2
example; If SSC
is 04h.
Decay Step Number: This register defines the number of steps to be used for the decay of MU where each step has a
period of SS taps (see SSC
Filter Length (512 or 1024) - [Decay Step Number (NS
For example, if NS
256 taps for a filter length of 512 taps.
7
7
is zero.
Note: Bits marked with “0” are reserved bits and should be written “0”.
7-0
Flat Delay (FD
FD
NS
6
6
6
0
x 8 taps. For example; if FD
6
6
7-0
is: 0
2-0
FD
NS
5
5
5
0
7-0
= 4, then MU is reduced by a factor of 2 every 64 taps of the FIR filter. The default value of SSC
5
5
7-0
=4 and SSC
FD
)
7-0
FD
4
2-0
4
NS
4
0
4
). The start of the exponential decay is defined as:
64 in normal mode and 0
4
2-0
=4, then the exponential decay start value is 512 - [NS
NS
FD
3
3
3
FIR Filter Length (512 or 1024 taps)
7-0
0
3
3
= 5, then MU=2
SSC
FD
NS
2
2
2
2
2
2
SSC
7-0
FD
-16
NS
1
1
FD
1
) x Step Size (SS)] where SS = 4 x2
1
1
for the first 40 taps of the echo canceller FIR filter. The valid
7-0
1
128 in extended-delay mode. The default value of FD
SSC
FD
NS
0
0
0
0
0
0
Read/Write Address: 04h + Base Address
Read/Write Address: 24h + Base Address
Read/Write Address: 07h + Base Address
Read/Write Address: 06h + Base Address
Read/Write Address: 27h + Base Address
Read/Write Address: 26h + Base Address
Step Size (SS)
Number of Steps (NS
7-0
Advance Information
x SS] = 512 - [4 x (4x2
SSC
-16
). The delay is defined
2-0
Power Reset Value
Power Reset Value
Power Reset Value
.
00h
04h
00h
SSC
7-0
Time
)
2-0
. For
4
)] =
2-0
7-