T8531A/T8532 Agere Systems, Inc., T8531A/T8532 Datasheet - Page 22

• Manufacturer Part Number: T8531A/T8532
• Description: Multichannel Programmable Codec Chip Set
• Manufacturer: Agere Systems, Inc.

Codec Chip Set
Chip Set Functional Description
(continued)
Start-Up After Internal Reset
Autocalibration
Autocalibration is an analog self-test and trimming pro-
cedure controlled by the DSP core. Sine wave signals
are generated in the receive direction. These signals
are looped back at the analog side of the T8532, and
the return signal amplitudes are measured in the trans-
mit path. This procedure provides on-the-spot fault
coverage of the transmit and receive paths. It also cali-
brates the octal devices by modifying the gain on each
channel. Channel four of the T8532 is the only channel
trimmed at the factory for absolute gain accuracy.
When autocalibration is run, all channels are trimmed
with reference to channel four. That is, the gain on
each channel is adjusted so that its absolute gain is
equivalent to that of the trimmed channel. Performing
trimming in this manner provides channel-to-channel
gain matching of better than 0.01 dB. This is a much
better performance than could be achieved using con-
ventional trimming. Trimmed values are placed in data
storage, and absolute gain values are then modified
accordingly any time the absolute gain register is
changed.
The calibration sequence measures the looped-back
power result and compares it to the calibrated channel.
The trim window is 0.2 dB. If any channel exhibits a
power value which is greater than 0.2 dB, the calibra-
tion procedure sets a failure flag for that channel. Trim-
ming will not be performed on the failed channel, and
the channel’s trimmed gain will be left at 0 dB. The
failed channel, therefore, is left in its previous state and
can still be used. The results of calibration are held in
RAM address 0x07F4 for transmit (pass 1) and 0x07F5
for receive (pass 2). A bit is set high for every failed
channel.
The preceding section discussed the sequence of
instructions that must be followed in order to properly
configure the T8531A for normal operation. The auto-
calibration procedure is mandatory after hardware
reset.
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(continued)
User Test Features
This section outlines the T8531A test features and
architecture. For more information on the line-test
capabilities, see the T8531A/T8532 User Manual and
the T8531A ROM Routines User Manual .
Off-Line Programmable System Test Capability
The T8531A has a standard 4-pin test access port
known as JTAG that can be used for testing and
debugging. The user has the option of downloading
custom firmware to the DSP engine RAM via the JTAG
port, and running it in the DSP engine in place of the
normal ROM-based code. The DSP16 hardware devel-
opment tool provides a powerful user interface for real-
time code development and debug. The user can also
execute the self-test ROM routine which exercises sig-
nificant portions of the T8531A and T8532 devices.
On-Line Per-Channel Test Capability
In addition to the active (i.e., normal voice processing
functions) and inactive routines, the user can select the
routines listed in Table 41 by altering the TX and RX
routines address in the time-slot information table (see
Table 6).
Inactive Mode with Loopback
This is a pair of routines that are used for the TX and
RX parts of the channel. Data from SDR is looped back
without modification to SDX.
Self-Test and Line-Test Routines
The following routines can be used to test the codec,
SLIC, relays, discretes, and line functionality.
Tone Generation
In tone generation mode, the RX part of the channel is
used to send a sine wave signal out to the line. The
sine wave can be up to 4 kHz in frequency, and up to
1024 points long. The RX filter is not implemented in
tone generation.
Agere Systems Inc.
May 2001