參數(shù)資料
型號(hào)： AM79Q021VC
廠商： Electronic Theatre Controls, Inc.
英文描述： Quad Subscriber Line Audio-Processing Circuit (QSLAC) Devices
中文描述： 四用戶線路音頻處理電路（QSLAC）設(shè)備
文件頁(yè)數(shù)： 36/68頁(yè)
文件大小： 1361K
代理商： AM79Q021VC
36
Am79Q02/021/031 Data Sheet
Figure 13. Robbed-Bit Frame
Default Filter Coefficients
The QSLAC device contains an internal set of default
coefficients for the programmable filters. These coeffi-
cients were determined to allow reasonable system
performance for initial power-up non-programmed situ-
ations, such as may exist before a system processor
has opportunity to program any coefficients.
The default filter coefficients are calculated assuming
an Am7920 SLIC with 50
protection resistors, a
178 k
transversal impedance (ZT), and a 90.5 k
re-
ceive impedance (ZRX). This SLIC has a transmit gain
of 0.5 (GTX) and a current gain of 500 (K1). The trans-
mit relative level is set to +0.28 dBr, and the receive rel-
ative level is set to
–
4.39 dBr. The equalization filters (X
and R) are not optimized. The balance filter was de-
signed to give acceptable balance into a variety of im-
pedances. The nominal input impedance was set to
815
. If the SLIC circuit differs significantly from this
design, the default filters cannot be used and must be
replaced by programmed coefficients.
To obtain this above-system response, the default filter
coefficients are set to produce these values:
GX gain = +6 dB, GR gain =
–
8.984 dB
AX gain = 0 dB, AR gain = 0 dB
R filter: H(z) = 1, X filter: H(z) = 1
Z filter: H(z) = 0, B filter H(z) = 0
AISN = cutoff
Notice that these default coefficient values are retained
in a read-only memory area within the QSLAC device,
and those values cannot be read back using any data
commands. When the device is selected to use default
coefficients, it obtains those values directly from the
read-only memory area, where the coefficient read
operations access the programmable random access
data memory only. If an attempt is made to read back
any filter values without those values first being written
with known programmed data, the values read back
are totally random and do not represent the default or
any other values.
COMMAND DESCRIPTION AND FORMATS
Microprocessor Interface Description
A microprocessor can program and control the QSLAC
device using the MPI. Data programmed previously
can be read out for verification.
Commands assign values to the following channel
parameters:
Transmit time slot
Receive time slot
Transmit clock slot
Receive clock slot
Transmit gain
Receive loss
B-filter coefficients
X-filter coefficients
R-filter coefficients
Z-filter coefficients
AISN coefficient
Read/Write SLIC Input/Output
SLIC Input/Output Direction
Select A-law, μ-law, or linear code
Select Transmit PCM Port A or B or both
Select Receive PCM Port A or B
Programmed/Default B filter
Programmed/Default Z filter
Programmed/Default X filter
Programmed/Default R filter
Programmed/Default GX filter
Programmed/Default GR filter
Enable/disable AX amplifier
Enable/disable AR amplifier
Select test states
Select Active or Inactive (standby) state
Commands are provided to read values from the
following channel monitors:
SLIC status
Transmit PCM data
PCLK
FS
Normal Frame (Not Robbed-Bit)
PCLK
FS
Robbed-Bit Frame
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