XR72L52 Datasheet, PDF (393/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L52
REV. 1.0.1
FIGURE 161. BEHAVIOR OF TRANSMIT OVERHEAD DATA INPUT INTERFACE SIGNALS BETWEEN THE XRT72L52 AND
THE TERMINAL EQUIPMENT (FOR METHOD 2)
TxInClk
TxOHFrame
TxOHEnable
TxOHIns
TxOH
TxOHEnable Pulse # 0
TxOHEnable Pulse # 32
MA Byte, Bit 7
Terminal Equipment
samples “TxOHFrame” and
“TxOHEnable” being “HIGH”
Terminal Equipment counts the number of
TxOHEnable pulses. At “pulse # 32” the Terminal
Equipment asserts the “TxOHIns” signal and places the
desired data on TxOH.
XRT72L5x samples TxOH
here.
6.2.3 The Transmit E3 HDLC Controller
The Transmit E3 HDLC Controller block can be used to transport Message-Oriented Signaling (MOS) type
messages to the remote terminal equipment as discussed in detail below.
NOTE: While executing this particular write operation, the user should write the binary value "000xx110b" into the Tx Con-
troller block), please see Section 4.2.3.2.
6.2.3.1 Message-Oriented Signaling (e.g., LAP-D) processing via the Transmit E3 HDLC Controller
The LAPD Transmitter (within the Transmit E3 HDLC Controller Block) allows the user to transmit path mainte-
nance data link (PMDL) messages to the remote terminal via the Outbound E3 Frames. In this case the mes-
sage bits are either inserted into and carried by the NR or the GC bytes, within the Outbound E3 frames. The
on-chip LAPD transmitter supports both the 76 byte and 82 byte length message formats, and the Framer IC
allocates 88 bytes of on-chip RAM (e.g., the Transmit LAPD Message buffer) to store the message to be trans-
mitted. The message format complies with ITU-T Q.921 (LAP-D) protocol with different addresses and is pre-
sented below in Figure 162.
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