XRT72L56 Datasheet, PDF (308/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
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PRELIMINARY
FIGURE 119. A SIMPLE ILLUSTRATION OF THE TRANSMIT E3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO
OTHER FUNCTIONAL BLOCKS
Transmit HDLC
Controller/Buffer
Transmit Overhead
Data Input Interface
Transmit Payload Data
Input Interface
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To Transmit E3 LIU Interface Block
In addition to taking data from multiple sources and
multiplexing them, in appropriate manner, to create
the outbound E3 frames, the Transmit E3 Framer
block has the following roles.
• Generating Alarm Conditions
• Generating Errored Frames (for testing purposes)
• Routing outbound E3 frames to the Transmit E3 LIU
Interface block
Each of these additional roles are discussed below.
5.2.4.2.1 Generating Alarm Conditions
The Transmit E3 Framer block permits the user to, by
writing the appropriate data into the on-chip registers,
to override the data that is being written into the
Transmit Payload Data and Overhead Data Input In-
terfaces and transmit the following alarm conditions.
• Generate the Yellow Alarms (or FERF indicators)
• Manipulate the A-bit, by forcing it to “0”.
• Generate the AIS Pattern
• Generate the LOS pattern
• Generate FERF (Yellow) Alarms, in response to
detection of a Red Alarm condition (via the Receive
Section of the XRT72L56).
The procedure and results of generating any of these
alarm conditions is presented below.
The user can exercise each of these options by writ-
ing the appropriate data to the Tx E3 Configuration
Register (Address = 0x30). The bit format of this reg-
ister is presented below.
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx
BIP-4
Enable
TxASourceSel[1:0]
TxNSourceSel[1:0]
Tx AIS
Enable
Tx LOS
Enable
Tx FAS
Source
Select
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit-fields 1 and 2 permit the user to transmit various
alarm conditions to the remote terminal equipment.
The role/function of each of these two bit-fields within
the register, are discussed below.
5.2.4.2.1.1 Tx AIS Enable - Bit 2
This read/write bit field permits the user to force the
transmission of an AIS (Alarm Indication Signal) pat-
tern to the remote terminal equipment via software
control. If the user opts to transmit an AIS pattern,
then the Transmit Section of the Framer IC will begin
to transmit an unframed all ones pattern to the re-
mote terminal equipment. Table 55 presents the rela-
tionship between the contents of this bit-field, and the
resulting Framer action.
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