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January 24, 2005
is open prior to driving signals into the BNC connectors. An
output level of 0dBm from the CODEC is required to provide
full scale ringing when operating from -100V battery.
External Ringing Source
Using an external function generator at J9 provides the most
control of the ringing waveform. The flexibility of the ringing
interface can be fully exercised by the function generator.
Trapezoidal Ringing
A logic level square wave, at J9, with 50% duty cycle will be
shaped by the components R
TRAP
and C
TRAP
when this
jumper position is selected. The components shipped with
the evaluation board will result in a 75V
RMS
trapezoidal
ringing waveform when operating from a -100V battery.
Ring Trip Control
Three very distinct actions occur when the device detects a
ring trip. First, the DET output is latched low. The latching
mechanism eliminates the need for software filtering of the
detector output. The latch is cleared when the operating
mode is changed externally. Second, the VRS input is
disabled, removing the ring signal from the line. Third, the
device is internally forced to the forward active mode,
however, low battery is not automatically selected upon ring
trip, and must be switched manually using the BSEL toggle
switch.
AC Transmission Tests
Description
Tests of the AC transmission parameters of the SLIC and the
CODEC can be performed individually, or as a complete 2W
to PCM line circuit. Jumpers are used to complete the
analog signal interface between the RSLIC and the CODEC
as shown in Table 3. The RSLIC and CODEC gain equations
and target values are contained in Section 3: AC
Transmission Theory and Design.
Test Set-up for RSLIC and CODEC Gains
Basic tests of the RSLIC and CODEC AC gain parameters
can be performed using a signal generator and standard AC
voltmeters, or a complete suite of PCM4 tests can be
performed on the RSLIC and the CODEC separately. The
RSLIC PCM4 tests use the A-A tests. The CODEC R
X
and
T
X
gain tests use the PCM4 A-D and D-A tests.
For RSLIC gain tests, the R
X
AC test input is connected to
the VREC BNC (RSLIC receive input) and the 2W AC test
output is measured at the tip-ring terminals. The RSLIC
analog 4W transmit output is measured at the VXMIT BNC.
A summary of RSLIC and CODEC tests is provided in Table
8.
The following analog input and output characteristics must
be considered when performing AC testing.
RSLIC analog I/O:
• Rx input impedance (VREC) is >30k
Ω
), and is AC
coupled.
• Tip to ring AC impedance is 600
Ω
. A DC potential of up
to 48VDC is present. AC coupling is required.
• Tx output impedance (at VXMIT) is <10
Ω
; AC coupled.
CODEC analog I/O
• Tx input (at VXMIT) is >50k
Ω,
DC coupled.
• Rx output (at VREC) is <20
Ω
, DC coupled.
Care must be given to the proper selection of analog
impedances on the PCM4 analog R
X
and T
X
ports when
performing PCM4 AC gain tests.
PCM4 Set-up
Analog PCM4 testing of the RSLIC parameters is performed
using the analog I/O on the front panel. CODEC A-D and D-
A testing with the PCM4 requires the use of the digital I/O
connections to the evaluation board as indicated in the table
below.
Front panel cable lengths should be equal, and should be as
short as possible to prevent delay-induced errors.
The PCM4 General Parameter settings in the following table
should be used to configure the digital interface to the
CODEC prior to D-A and A-D testing.
TABLE 6. PCM4 DIGITAL I/O CONNECTION
PCM4 DIGITAL PORT
EVALUATION BOARD DIGITAL
PORT
Rx Signal
J10 - DT
Tx Signal
J11 - DR
Frame Sync
J12 - F.S.
Tx Clock
J13 - CKL
TABLE 7. PCM4 GENERAL PARAMETER SETTINGS
PCM4 GENERAL PARAMETER
SETTING
1 - DIGITAL CONFIGURATION
11, 23
2 - FRAME SELECTION
14, 24, 31
3 - DIGITAL TX INTERFACE
13, 22, 31
4 - DIGITAL RX INTERFACE
13, 22
5 - DIGITAL WORDS IN TX FRAME
11, 22
6 - TX ERROR INSERTION
11
7 - PCM ENCODING (A-law)
11, 21
8 - SCANNER PARAMETER
11, 21
9 - SPECIAL PARAMETER
11, 13, 16, 22, 23, 27,
33, 35
Application Note 1168
