AccessRunner ADSL-USB Modem Device Set Data Sheet
2.3.2
CX11627 ADDP Description
The CX11627 ADSL DMT Data Pump (ADDP) is a T1.413 Issue 2, G.992.1, and G.992.2 compliant custom digital signal
processing (DSP) chip built specifically for DMT ADSL transmission for use in ADSL modems. The CX11627 operates from
+2.5V for core operation and +3.3V for interface circuit operation. A block diagram of the CX11627 ADDP is shown in Figure
2-2.
ATM Transmission Convergence
In the transmit direction, the ATM Transmission Convergence (TC) block embeds ATM cells into the serial data stream being
fed into the digital interface, i.e., the P5200 UIC. In the receive direction, this block extracts the ATM cell boundaries from the
serial data stream coming from the digital interface To reduce traffic on the USB, the TC block performs idle cell insertion in
the transmit direction and idle cell deletion and header error correction in the receive direction.
Digital Interface
The Digital Interface (DI) Transmit Block performs the following functions: transmit data multiplexing and buffering, fast and
interleave data stream framing, transmit data synchronization control, eoc/aoc insertion, CRC encoding, scrambling, FEC
encoding, and data interleaving.
The DI Receive Block performs the following functions: data de-interleaving, FEC decoding, descrambling, CRC check,
receive data synchronization and receive clock generation, demultiplexing and buffering of receive data and receive eoc/aoc.
QAM Encoder/Decoder
The QAM Encoder/Decoder performs the following functions: constellation encoding, clock recovery, receive gain
compensation, frequency domain equalization (FEQ), slicing, and constellation decoding. The block also performs other
functions such as frequency domain signal processing, signal power, error power averaging and computations related to
frequency domain training.
FFT
The FFT performs IFFT for modulation of the transmit symbol, and FFT for demodulation of the receive symbol.
Analog Front End Interface
The Analog Front End (AFE) interface performs the following functions: transmit signal filtering, time domain equalization, and
time domain signal power averaging, and echo cancellation (EC).
Microcontroller Interface
The microcontroller interface enables the P5200 UIC to set parameters to control DSP sequencing and to read/write
coefficients or data.
CX11627 ADSL DMT Data Pump (ADDP)
Digital
Interface (DI)
QAM Encoder/Decoder
FFT
AFE Interface
Bit
Parser
and QAM
Encoder
DI
Transmit
Block
Transmit
Filter
DAC
Intf
IFFT
CX20431
Analog
Front End
(AFE)
EC
ATM
TC
P5200
USB
Interface
Controller
(UIC)
QAM
Decoder
and Bit
Parser
DI
Receive
Block
Time
Domain
Equalizer
ADC
Intf
FEQ
FFT
Microcontroller
Interface
100427 F2-2 BD 11627
Figure 2-2. CX11627 ADDP Block Diagram
2-4
Conexant
100427B
CONEXANT [ CONEXANT SYSTEMS, INC ]
