XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
PRELIMINARY
REV. P1.0.1
84
The following sections discuss each functional
sub-block of the Transmit UTOPIA Interface Block in
detail. These sections will discuss the many features
associated with the Transmit UTOPIA Interface block
as well as how to select/configure these features in
order to suit particular application needs. Detailed
discussion of Single-PHY and Multi-PHY operation
will each be presented in its own section even though
it involves the use of all of these functional blocks.
2.1.2.1Transmit UTOPIA Bus Input Interface
The Transmit UTOPIA input interface complies with
UTOPIA Level 2 standard interface (e.g., the Transmit
UTOPIA can support both Single-PHY and Multi-PHY
operations.) Additionally, the UNI provides the option
of varying the following features associated with the
Transmit UTOPIA Bus Interface.
Transmit UTOPIA Data Bus width of 8 or 16 bits
The cell size (e.g., the number of octets being
processed per cell via the UTOPIA bus)
The handling of errored cells received from the
ATM Layer processor
A discussion of the operation of the Transmit UTOPIA Bus
Interface along with each of these options will be presented
below.
2.1.2.1.1The Pins of the Transmit UTOPIA Bus
Interface
The ATM Layer processor will interface to the Transmit
UTOPIA Interface block via the following pins.
TxUData[15:0]—Transmit UTOPIA Data Bus Input
pins
TxUAddr[4:0]—Transmit UTOPIA Address Bus
Input pins
TxUClk—Transmit UTOPIA Interface block clock
input pin
TxUSoC—Transmit “Start of Cell” indicator input
pin
TxUPrty—Transmit UTOPIA—Odd Parity Input pin
TxUEn
—Transmit UTOPIA Data Bus—Write
Enable input pin
TxUClav—TxFIFO Cell Available
Each of these signals are briefly discussed below.
F
IGURE
4. F
UNCTIONAL
B
LOCK
D
IAGRAM
OF
THE
T
RANSMIT
UTOPIA B
LOCK
TxUData [7:0]
TxUSoC
Tx Utopia
FIFO Manager
TxUtopia
Registers
D[15:0]
A[8:0]
Status Signals
Control Signals
Tx Utopia
Cell FIFO
TxUSoC
TxUClk
TxUtopia Interrupt
TxUClav
Controls from
Registers
(To Pin)
(To Interrupt block)
Microprossor
Interface
TxCel Present (to Tx Cell Processor
Status Bits to Registers
To Tx Cell Processor
TxFRdClk
TRdEn
TxUEn
TxUAddr [4:0]
TxUData [15:0]
TxUData [7:0]