XRT79L71
PRELIMINARY
293
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
illustration of the Transmit Direction circuitry whenever the XRT79L71 has been configured to operate in the E3
Clear-Channel Framer Mode, with the Transmit Overhead Data Input Interface block highlighted.
Some Background Information
In order to fully understand the role of the Transmit Overhead Data Input Interface, some background
information needs to be discussed first.
are payload bits and the remaining 12 bits are overhead bits. The XRT79L71 has been designed to handle
and process both the payload type and overhead bytes of bits/bytes for each E3 frame. Within the XRT79L71,
the Transmit Payload Data Input Interface Block (which was discussed in considerable detail in
accept the payload data from the "System-Side" Terminal Equipment. Likewise, the Transmit Overhead Data
Input Interface block has been designed to handle and process the overhead bits.
Accepting and Inserting E3 Overhead Bits via the Transmit Overhead Data Input Interface
By default, the Transmit E3 Framer block will be configured to internally generate and insert all of the overhead
bytes within its outbound E3 data-stream.
More specifically, the Transmit E3 Framer block will internally
generate the E3 overhead bytes by doing all of the following, as presented below in Table 38.
FIGURE 138. ILLUSTRATION OF THE FUNCTIONAL BLOCK DIAGRAM OF THE TRANSMIT DIRECTION CIRCUITRY, WHEN-
EVER THE
XRT79L71 HAS BEEN CONFIGURED TO OPERATE IN THE E3, ITU-T G.751 CLEAR-CHANNEL FRAMER
MODE (WITH THE TRANSMIT OVERHEAD DATA INPUT INTERFACE BLOCK HIGHLIGHTED)
Transmit
Payload Data
Input
Interface
Block
Transmit
Payload Data
Input
Interface
Block
Transmit
DS3/E3
Framer
Block
Transmit
DS3/E3
Framer
Block
Tranmit
DS3/E3
LIU Block
Tranmit
DS3/E3
LIU Block
TxSer
TxNib[3:0]
TxInClk
TRING
TTIP
Transmit
Overhead Data
Input Interface
Block
Transmit
Overhead Data
Input Interface
Block
TxOHClk
TxOHIns
TxOHInd
TxOH
TxOHEnable
TxOHFrame
TxNibClk
TxFrame
Tx LAPD
Controller
Block
Tx LAPD
Controller
Block
From Microprocessor
Interface Block
Tx LAPD
Buffer
(90 Bytes)
Tx LAPD
Buffer
(90 Bytes)