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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—UTOPIA Level 2
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
270
Reference Number: 306262-004US
the IXP45X/IXP46X network processors’ control plane processors. The module’s user-
accessible features are described in the Intel
®
IXP400 Software Programmer’s Guide
and may be a subset of the features described in this section.
The UTOPIA Level 2 Transmit interface transfers ATM cells to one or more UTOPIA-
compliant physical devices. In multiple-PHY (MPHY) mode, the UTOPIA Level 2 transmit
interface uses a round-robin polling routine to poll the various physical interfaces using
the five transmit address lines (UTP_OP_ADDR) to determine which physical interfaces
are ready to accept data transfers. The result of the polling is provided as status to the
Network Processor Engine.
The Transmit Module is the entity, within the UTOPIA coprocessor, that implements this
functionality. The Transmit Module will poll a programmable number of physical
interfaces as defined by the Transmit Address Range (TXADDRRANGE) register.
If five physical interfaces are connected to the UTOPIA Level 2 interface, a value of four
can be programmed into the Transmit Address Range (TXADDRRANGE) register by the
Network Processor Engine Core. The polling will always begin at logic address 0 and poll
sequentially to the value contained in the Transmit Address Range (TXADDRRANGE)
register.
To allow the most flexibility, a logical address to physical address table is provided. The
look-up table makes it possible for the five addresses — that were called out, above —
not to be in sequential order. For example, the following logical to physical address map
could be used for the above example of five physical interfaces.
• Logical Address 0 => Physical Address 3 => UTP_OP_ADDR lines = 00011
• Logical Address 1 => Physical Address 5 => UTP_OP_ADDR lines = 00101
• Logical Address 2 => Physical Address 7 => UTP_OP_ADDR lines = 00111
• Logical Address 3 => Physical Address 9 => UTP_OP_ADDR lines = 01001
• Logical Address 4 => Physical Address 22 => UTP_OP_ADDR lines = 10110
Once the physical address is driven to all physical interfaces, using the UTP_OP_ADDR
signals, the physical interface is ready to accept a cell. The physical interface is
configured to the address signals that match the values contained on the
UTP_OP_ADDR signals and responds to the UTOPIA Level 2 interface on the IXP45X/
IXP46X network processors by driving the UTP_OP_FCI (a.k.a TX_FULL_N/TX_CLAV)
signal to inform the UTOPIA Level 2 Interface that the physical interface is ready to
receive a cell.
The Transmit Port Status (TXPORTSTAT) register — contained within the Transmit
Module — stores the polling result for each of the physical interfaces. The Network
Processor Engine core uses the values stored in the Transmit Port Status
(TXPORTSTAT) Register to select a physical interface that is ready to complete a
transfer and loads the Transmit FIFO.
The Transmit FIFO informs the Transmit Module that a cell is ready to be transmitted to
a specific physical interface. The Transmit Module will then remove the cell information
from the Transmit FIFO and begin transmitting the data to the specified physical
interface. It is important to note that the NPE code will send to the Transmit Module the
logical port address of the physical interface to be selected along with the cell data.
This feature allows the NPE to have full control over transmitted data based upon the
polling status returned from the hardware.
While transmitting the data, an optional head-error correction (HEC) value can be
calculated from the header and inserted into the data stream. The HEC generation unit
takes the header data and uses the data with an internal, 8-bit HEC cyclical redundancy