XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
60
Bit 7—Line Loop Back Mode
This “Read/Write” bit-field allows the user to config-
ure the UNI to operate in the “Line Loopback” mode.
This is an operating mode that is available via the
UNI Test and Diagnostic Features. When the UNI is
operating in this mode, then the Transmit stream from
the TxPOS and TxNEG pins, are (internally) looped
back into the Receive RxPOS and RxNEG input pins.
Writing a “1” to this bit-field enables the Line Loop-
back Mode. Writing a “0” to this bit-field disables the
Line Loopback Mode.
For more information on the Line Loopback Mode of
operation, please see Section 4.1.1.
Bit 6—Cell Loop Back Mode
This “Read/Write” bit-field allows the user to config-
ure the UNI to operate in the “Cell Loopback” mode.
This is an operating mode that is available via the
UNI Test and Diagnostic Features. When the UNI is
operating in this mode, then the ATM Cells that are
delineated and pass through the Receive Cell Pro-
cessor will be routed directly (internally) to the Tx
FIFO (within the Transmit UTOPIA Interface block).
Writing a “1” to this bit-field enables the Cell Loop-
back Mode. Writing a “0” to this bit-field disables the
Cell Loopback Mode.
For more information on the Cell Loopback Mode of
operation, please see Section 4.1.3.
Bit 5—PLCP Loop Back Mode
This “Read/Write” bit-field allows the user to config-
ure the UNI to operate in the “PLCP Loopback”
mode. This is an operating mode that is available via
the UNI Test and Diagnostic Features. When the UNI
is operating in this mode, then the PLCP frames that
have been generated by the Transmit PLCP Processor,
will be routed directly (internally) to the Receive
PLCP Processor.
Writing a “1” to this bit-field enables the PLCP Loop-
back Mode. Writing a “0” to this bit-field disables the
PLCP Loopback Mode.
For more information on the PLCP Loopback Mode
of operation, please see Section 4.1.2
Bit 4—Reset
This “Read/Write” bit-field allows the local μP/μC to
command a reset of the entire UNI IC. When the UNI
is reset, both the TxFIFO and the RxFIFO are flushed,
and all on-chip registers are reset to their default val-
ues, and all configurations are automatically set to
their default conditions.
Writing a “1” to this bit-field will reset the UNI IC.
Writing a “0” to this bit-field imposes no change in the
UNI IC.
Bit 3—Direct Mapped ATM/PLCP Mode* Selection
This “Read/Write” bit field allows the user to config-
ure the UNI to operate in the “Direct Mapped ATM” or
in the “PLCP” Mode of operation. Writing a “1” to this
bit-field causes the UNI to be operating in the “Direct
Mapped ATM” mode. Whereas, writing a “0” to this
mode causes the UNI to operate in the “PLCP
Mode”. When the UNI is operating in the Direct
Mapped ATM Mode, both the Transmit and Receive
PLCP Processor blocks will be disabled. Conse-
quently, in the Transmit Section, ATM cells will not be
packed into PLCP Frames prior to transmittal to the
Transmit DS3 Framer. ATM cells will proceed from
the Transmit Cell Processor, directly to the Transmit
DS3 Framer. The ATM Cell data will be “directly-
mapped” into the payload portions of the outgoing
DS3 frames. In the Receive Section, the payload por-
tions of the incoming DS3 frames will be routed di-
rectly to the Receive Cell Processor for further pro-
cessing. Please see Sections 6.3.3.9 and 7.3.2.1.2
for a more detailed discussion into Direct Mapped
ATM mode operation.
Bit 2—M13/C-Bit* (DS3 Frame Format) Selection
This “Read/Write” bit-field allows the user to config-
ure the UNI (e.g., the Transmit DS3 Framer and the
Receive DS3 Framer) to operate in either the C-bit
Parity or in the M13 frame format.
Writing a “0” to this bit-field configures the Transmit
and Receive DS3 Framer to operate in the C-bit Pari-
ty frame format. Writing a “1” to this bit-field config-
ures the Transmit and Receive DS3 Framers to oper-
ate in the M13 frame format. For more information on
these two framing formats, please see Section 6.4.2.
Bits 1, 0—TimRefSel[1, 0] (Timing Reference
Select—Transmit PLCP Processor and Transmit
DS3 Framer)
These two “Read/Write” bit-fields allow the user to
specify the following parameters:
The Timing Reference for the Transmit DS3 Framer
The Timing Reference for the Transmit PLCP
Processor
The “Transmit PLCP Frame Stuff Control” Algorithm
employed
The relationship between these two bit-fields and
these three parameters are tabulated below.