MT90221 Zarlink Semiconductor, MT90221 Datasheet - Page 19

• Manufacturer Part Number: MT90221
• Description: Quad Inverse Multiplexing For Atm (IMA) Device With Flexible Ima And Uni Mode
• Manufacturer: Zarlink Semiconductor

MT90221
Section 5 describes the UTOPIA Interface in more
detail.
2.2
The Transmit Convergence (TC) function is common
for both the IMA and UNI modes. It integrates the
circuitry to support ATM cell payload scrambling,
HEC generation and the generation of Idle/Filler/ICP
cells for use with the T1 and/or E1 trunks. Each of
the four MT90221 ATM TC circuits can use the
polynomial X
field. The MT90221 ATM cell payload scrambling
function can be disabled.
The ITU I.432 polynomial X
generate the HEC field of the ATM cell. By default,
the ATM Forum polynomial X
to the calculated HEC octet. The addition of the ATM
Forum polynomial can be disabled.
10
ATM In
The ATM Transmission Convergence
43
+ 1 to scramble the ATM cell payload
from IDCR Generator
UTOPIA L2 Interface
Cell_In_Control
Micro I/F
Figure 3 - Functional Block Diagram -Transmitter in IMA Mode
8
6
+ X
+ X
2
4
+ X + 1 is used to
+ X
2
+ 1 is added
Filler Cell
Idle Cell
ICP Cell Group 1
ICP Cell Group 2
ICP Cell Group 3
ICP Cell Group 4
Next ICP Cell Group 1
Next ICP Cell Group 2
Next ICP Cell Group 3
Next ICP Cell Group 4
ICP Cell Buffer RAM
TX Utopia FIFO
TX Utopia FIFO
(see Note 1)
(see Note 1)
(see Note 1)
FIFO Link 0
FIFO Link 1
FIFO Link 3
Transmitter
Cell RAM
Group 0
Group 3
The resulting calculation is then over-written on the
HEC field and the ATM cell is ready (i.e., complies
with the IMA transmit protocol) for transmission over
the PCM Interface.
In cases where the TC block requests a cell to be
transferred to any of the PCM Interfaces and the TX
UTOPIA FIFO has no cell ready for transmission,
then the TC block will automatically send an IDLE
cell (in UNI) or a Filler cell (in IMA mode) to the line.
The default values for the Idle and the Filler cells
comply with the ATM IMA Specification and are pre-
loaded in the MT90221 following a reset. The TX
Cell RAM Control register can be used to re-
initialize the TX Cell RAM.
2.2.1
The internal TX Cell Ram can hold up to 64 cells.
The following six cells are reserved for MT90221
operation:
•
one ICP cell for each IMA Group for a total of
four cells
Round Robin Scheduler
and Adaptive Shaper
and FIFO Selection
ICP Cell Modifier and
ICP Cell Modifier and
ICP Cell Modifier and
TX Cell Ram and TX FIFO Length
to Cell_In_Control
ICP Cell Handler
Cell Scrambling
Cell Scrambling
Cell Scrambling
(1 of 4)
Note 1: This FIFO is the
TX UTOPIA FIFO when
the link is configured in
UNI Mode and it is the
TX LINK FIFO when it is
configured in IMA Mode.
IDCR Generator
Transmitter
Link Timing
Reference
(1 of 4)
P/S
P/S
P/S
Streams
Serial
Link 0
Link 1
Link 3