Le58083
Data Sheet
9A/9Bh Write/Read IIR Z Filter Coefficients (IIR only)
MPI Command
R/W = 0: Write
R/W = 1: Read
This command writes/reads the IIR filter section only, without affecting the FIR.
D7
D6
0
D5
D4
1
D3
D2
0
D1
D0
R/W
Command
1
0
1
1
I/O Data Byte 1
I/O Data Byte 2
I/O Data Byte 3
I/O Data Byte 4
I/O Data Byte 5
C45
C25
C26
C47
C27
m45
m25
m26
m47
m27
C35
C15
C16
C37
C17
m35
m15
m16
m37
m17
Cxy = 0 or 1 in the command above corresponds to Cxy = +1 or −1, respectively, in the equation below.
The Z-transform equation for the Z filter is defined as:
z5 • z6 • z7 • z–1
Hz(z) = z0 + z1 • z–1 + z2 • z–2 + z3 • z–3 + z4 • z–4 + ------------------------------------------
1 – z7 • z–1
Sample rate = 32 kHz
For i = 0 to 5 and 7
zi = C1i • 2–m1i{1 + C2i • 2–m2i[1 + C3i • 2–m3i(1 + C4i • 2–m4i)]}
z6 = C16 • 2–m16{1 + C26 • 2–m26
}
Power Up and Hardware Reset (RST) Values = 0190 0190 0190 0190 0190 0190 01 0190 (Hex)
(HZ(z) = 0)
See note under Command 80/81h on page 54.
Note:
Z6 is used for IIR filter scaling only. Its value is typically greater than zero but less than or equal to one. The input to the IIR filter
section is first increased by a gain of 1/Z6, improving dynamic range and avoiding truncation limitations through processing within
this filter. The IIR filter output is then multiplied by Z6 to normalize the overall gain. Z5 is the actual IIR filter gain value defined by
the programmed coefficients, but it also includes the initial 1/Z6 gain. The theoretical effective IIR gain, without the Z6 gain and
normalization, is actually Z5/Z6.
60
Zarlink Semiconductor Inc.
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