XRT72L56 Datasheet, PDF (258/486 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 96. AN ILLUSTRATION OF THE BEHAVIOR OF THE SIGNALS BETWEEN THE RECEIVE PAYLOAD DATA OUTPUT
INTERFACE BLOCK OF THE XRT72L56 AND THE TERMINAL EQUIPMENT (NIBBLE-MODE OPERATION).
Terminal Equipment Signals
RxOutClk
Rx_DS3_Clock_In
DS3_Data_In[3:0]
Rx_Start_of_Frame
Nibble [0]
XRT72L5x Receive Payload Data I/F Signals
RxOutClk
RxClk
RxNib[3:0]
RxFrame
Nibble [0]
DS3 Frame Number N
Note: RxFrame pulses high to denote
DS3 Frame Boundary.
DS3 Frame Number N + 1
Recommended Sampling Edge of Terminal
Equipment
Nibble [1]
Nibble [1]
4.3.6 Receive Section Interrupt Processing
The Receive Section of the XRT72L56 can generate
an interrupt to the Microcontroller/Microprocessor for
the following reasons.
• Change of State of Receive LOS (Loss of Signal)
condition
• Change of State of Receive OOF (Out of Frame)
condition
• Change of State of Receive AIS (Alarm Indicator
Signal) condition
• Change of State of Receive Idle Condition.
• Change of State of Receive FERF (Far-End
Receive Failure) condition.
• Change of State of AIC (Application Identification
Channel) bit.
• Detection of P-Bit Error in a DS3 frame
• Detection of CP-Bit Error in a DS3 frame
• The Receive FEAC Message - Validation Interrupt
• The Receive FEAC Message - Removal Interrupt
• Completion of Reception of a LAPD Message
4.3.6.1 Enabling Receive Section Interrupts
As mentioned in Section 1.6, the Interrupt Structure,
within the XRT72L56 contains two hierarchical levels.
• Block Level
• Source Level
The Block Level
The Enable state of the Block level for the Receive
Section Interrupts dictates whether or not interrupts
(if enabled at the source level), are actually enabled.
The user can enable or disable these Receive Sec-
tion interrupts, at the Block Level by writing the appro-
priate data into Bit 7 (Rx DS3/E3 Interrupt Enable)
within the Block Interrupt Enable register (Address =
0x04), as illustrated below.
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