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PRELIMINARY
DS3 UNI FOR ATM
XRT7245
REV. 1.03
183
Writing a ‘1’ to this bit-field will cause the Transmit
PLCP Processor to transmit G1 bytes with the FEBE
nibble value of ‘0h’ (independent of the number of
BIP-8 errors detected by the Receive PLCP Processor).
Writing a ‘0’ to this bit-field will cause the Transmit
PLCP Processor to transmit G1 bytes with the
correct FEBE count, as determined by the “Near-
End” Receive PLCP Processor.
6.3.3.6
Forcing a Yellow Alarm—Via Software
Control
The UNI allows the user to generate a “Yellow Alarm
(PLCP Version thereof)” via software control. In this
case, the Transmit PLCP Processor will generate a
“Yellow Alarm” by automatically setting the “RAI” bit
within each G1 byte to ‘1’. The user can exercise this
option by writing the appropriate bit to bit-field 3 of
the Tx PLCP G1 Byte Register (Address = 4Bh). The
bit format of this register follows.
Writing a ‘1’ to this bit-field forces the “PLCP—Yellow
Alarm” condition. Writing a ‘0’ to this bit-field allows
the state of the RAI bit to be based upon the framing
conditions of the “Near-End” Receive PLCP Processor.
6.3.3.7
Transmitting Data Link Messages
via the G1 Byte
The “Tx PLCP G1 Byte” Register contains three bit-
fields that can be used to support a 24 kbps data link
between the Near-End Transmit PLCP Processor,
and the Far-End Receive PLCP Processor, as depicted
below.
Whatever data is written into the three bit-fields will
appear in Bits 2–0 of the incoming G1 byte at the Far-
End Receive PLCP Processor.
6.3.3.8
Inserting POH Bytes via the TxPOH
Serial Input Port
The UNI allows the user to externally insert his/her
own PLCP POH (Path Overhead) bytes via a serial
input interface consisting of the pins: TxPOHIns, Tx-
POH, TxPOHFrame, and TxPOHClk. The user can
activate this serial input port by asserting the TxPO-
HIns input pin (e.g., setting it “high”). When this pin is
“l(fā)ow”, the UNI will internally generate the POH bytes.
However, when this pin is “high”, the user will be ex-
pected to provide his/her own value for the POH
bytes via the TxPOH input pin. The UNI will assert
(toggle “high”) the TxPOHFrame output pin when it
expects the MSB of the Z6 byte. The user will be ex-
pected to provide his/her value for the Z6 byte, with
the MSB first, in descending order. Immediately after
the LSB of the Z6 byte, the TxPOH Serial Input port
will be expecting the MSB of the Z5 byte, and so on.
The byte order that this serial input port expects is as
presented in Table 24. Once the TxPOH serial input
port has read in the LSB of the C1 byte, it will repeat
this sequence of bytes, beginning with the Z6 byte
first. The POH data will be serially latched into the
TxPOH input on the rising edge of the TxPOHClk
Tx PLCP G1 Byte Register (Address = 4Bh)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Unused
TxPLCP FEBE Mask
Yellow Alarm
LSS(2)
LSS(1)
LSS(0)
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
Tx PLCP G1 Byte Register (Address = 4Bh)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Unused
TxPLCP FEBE Mask
Yellow Alarm
LSS(2)
LSS(1)
LSS(0)
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
Tx PLCP G1 Byte Register (Address = 4Bh)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Unused
TxPLCP FEBE Mask
Yellow Alarm
LSS(2)
LSS(1)
LSS(0)
RO
RO
RO
R/W
R/W
R/W
R/W
R/W