
Z02201
V.22bis Data Pump with Integrated AFE
ZiLOG
28
Z02201
PS000902-0501
CONN_Mode
01F0
—
Connection Mode Register
This RAM location reports the connection type and speed established
after handshake is completed. The values for this location are the same
as those for Con
fi
g register, bits 0
–
6 (MODE):
Value
Data mode speci
fi
ed
8
V.22bis 2400 bps mode
9
V.22 1200 bps mode
B
Bell 212A 1200 bps mode
10
V.21 300 bps mode
11
Bell 103 300 bps mode
13
V.23 1200 bps Tx/75 bps Rx mode
14
V.23 75 bps Tx/1200 bps Rx mode
Notch Filter Coefficients
These RAM locations contain the notch filter coefficients. The notch filter
is a biquad section (2nd-order IIR) used during simultaneous transmission
and detection of tones (
Config register, bits 0
–
6 (MODE) is 4) to remove a
single transmitted tone from the received signal used by the tone detectors.
See the section
“
Simultaneous Transmission and Detection of Tones
”
on
page 1-35 for more information.
Notch
01A2-1A6
below
The default values for these locations are 0, 0, 0, 0, and 0x4000 respectively.
The default values cause the notch filter to not modify the received signal
used by the tone detectors. The data pump sets these locations to their
default values when the host sets Config register, bits 0
–
6 (MODE) to 4 to
begin simultaneous transmission and detection of tones.
The host must not modify these locations unless Config register, bits 0
–
6
(MODE) is 4.
To calculate the coefficients to remove a frequency
f
from the received
signal, use these following formulae where
,
r
= pole radius (0
≤
r<1), 0.9 is recommended
θ
= 2
π
f
/9600,
f
is the frequency (Hz) to be removed, (0
≤
f
<4800)
α
= (1-2rcos(
θ
)+r
2
)/(2-2cos(
θ)
)
Location
0x1A2 0x1A3
0x1A4 0x1A5 0x1A6
Name
b2 b1 a3 a2 a1
Formula
-r
2
2rcos(
θ
)
α
-2
α
cos(
θ
)
α
The cosine function is calculated in radians, not degrees.
Before writing the coefficients to data pump RAM, convert them to the
format used by the data pump by multiplying each coefficient by 16,383,
then round to the nearest 16-bit signed integer. For example, 2.0 becomes
32,766 (0x7FFE), -1.0 becomes -16,383 (0xC001), -2.0 becomes -32,766
(0x8002).
These formulae determine the coefficients of a biquad section with
symmetric zeroes, a zero radius of 1.0, a pole radius of r, and pole and zero
frequencies of
f
Hz.
See
“
Simultaneous Transmission and Detection of Tones
”
for more detail
and notch filter coefficients for the default frequencies detected by the
discrete tone detectors.
Table 15. Modem Data Pump Word De
fi
nitions (Continued)
Register & Address
(hex)
Default
Value
Function and Explanation