XR72L52 Datasheet, PDF (369/480 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
Finally, the XRT72L52 will pulse its TxOH_Ind output pin, one bit-period prior to it processing a given overhead
bit, within the Outbound E3 frame. Since the TxOH_Ind output pin (of the XRT72L52) is electrically connected
to the E3_Overhead_Ind, whenever the XRT72L52 pulses the TxOH_Ind output pin "High", it will also be driv-
ing the E3_Overhead_Ind input pin (of the Terminal Equipment) "High". Whenever the Terminal Equipment de-
tects this pin toggling "High", it should delay transmission of the very next E3 frame payload bit by one clock
cycle.
The behavior of the signals between the XRT72L52 and the Terminal Equipment for E3 Mode 2 Operation is il-
lustrated in Figure 148.
FIGURE 148. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L52 AND THE TERMINAL
EQUIPMENT (MODE 2 OPERATION)
Terminal Equipment Signals
E3_Clock_In
E3_Data_Out
Tx_Start_of_Frame
E3_Overhead_Ind
Payload[4238] Payload[4239]
FA1, Bit 7
FA1, Bit 6
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
TxSer
Payload[4238] Payload[4239]
TxFrameRef
TxOH_Ind
FA1, Bit 7
FA1, Bit 6
E3 Frame Number N
E3 Frame Number N + 1
Note: TxOH_Ind pulses high for
16 bit periods in order to
denote Overhead Data
(e.g., the FA1 and FA2 bytes)
Note: The FA1 byte will not be processed by the
Transmit Payload Data Input Interface.
Note: TxFrameRef pulses high to denote
E3 Frame Boundary.
How to configure the XRT72L52 to operate in this mode.
1. Set the NibIntf input pin "Low".
2. Set the TimRefSel[1:0] bit-fields (within the Framer Operating Mode Register) to "01" as depicted below.
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
Local Loop-back
BIT 6
DS3/E3*
R/W
R/W
0
0
BIT 5
Internal LOS
Enable
R/W
1
BIT 4
RESET
R/W
0
BIT 3
Interrupt
Enable Reset
R/W
1
BIT2
Frame Format
R/W
1
BIT 1
BIT 0
TimRefSel[1:0]
R/W
R/W
0
1
3. Interface the XRT72L52, to the Terminal Equipment, as illustrated in Figure 147.
6.2.1.3 Mode 3 - The Serial/Local-Timed/Frame-Master ModeBehavior of the XRT72L52
If the XRT72L52 has been configured to operate in this mode, then the XRT72L52 will function as follows.
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