mt90226ag ETC-unknow, mt90226ag Datasheet - Page 24

• Manufacturer Part Number: mt90226ag
• Description: 16/8 Port Tc Phy Device
• Manufacturer: ETC-unknow

24
2.2
The Transmit Convergence (TC) function integrates the circuitry to support ATM cell payload scrambling, HEC
generation and the generation of Idle cells for use with the T1/E1/J1 or DSL trunks. Each of the available ATM TC
circuits can use the polynomial X
scrambling function can be disabled.
The ITU I.432 polynomial X
Forum polynomial X
can be disabled. The resulting calculation is then written on the HEC field and the ATM cell is ready for transmission
over the flexible TDM Interface.
In cases where the TC block requests a cell to be transferred to any of the serial interfaces and the TX Link UTOPIA
FIFO has no cell ready for transmission, then the TC block will automatically send an IDLE cell to the line. The
default values for the Idle cells comply with the ATM Forum Specification and are pre-loaded in the MT90225/226
following a reset. The TX Cell RAM Control (0x0080) register can be used to re-initialize the TX Cell RAM. The
content of the Idle cell is pre-initialized with the header bytes set at 0x00, 0x00, 0x00 and 0x01. The payload bytes
are set to 0x6A.
Idle Cells are transmitted on the TC serial Interface until the bit corresponding to the link in the UTOPIA Input
Link PHY Enable (0x0050) register is set. Then, the ATM User cells are transferred from the Input UTOPIA
port to the TX serial port.
ATM In
The ATM Transmission Convergence
Cell_in_control
UTOPIA L2
6
Interface
+ X
and
Figure 4 - MT90225/226 Functional Block Diagram -Transmitter
4
+ X
8
+ X
2
+ 1 is added to the calculated HEC octet. The addition of the ATM Forum polynomial
43
2
+ X + 1 is used to generate the HEC field of the ATM cell. By default, the ATM
+ 1 to scramble the ATM cell payload field. The MT90225/226 ATM cell payload
TX Link Utopia FIFO 14
TX Link Utopia FIFO 15
TX Link Utopia FIFO 0
TX Link Utopia FIFO 1
Transmitter
Cell RAM
Zarlink Semiconductor Inc.
Controller
Insertion
Idle Cell
Output
and
P/S
P/S
P/S
P/S
Data Sheet
Streams
Link 14
Link 15
Serial
Link 0
Link 1