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PRELIMINARY
XRT79L71
228
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
1.
For normal operation, it is imperative that the user also make sure that Bit 7 (Receive LAPD Any) within this
register is set to "0".
2.
Once the user executes the above-mentioned step, then the Receive LAPD Controller will begin to extract out the
contents of any incoming LAPD/PMDL Message that is being transported via the DL bits within the incoming DS3
data-stream. In most cases, the Receive LAPD Controller block will simply begin to receive the Flag Sequence
octet which is originating from the remote terminal.
STEP 3 - Check and verify that the Receive LAPD Controller is receiving the Flag Sequence Octets
If the Receive LAPD Controller block is currently receiving the Flag Sequence octets within the incoming DS3
data-stream, then it will assert Bit 0 (Flag Present) within the Receive DS3 LAPD Status Register, as depicted
below.
STEP 4 - Enable the Receive LAPD Interrupt (Optional).
This step is optional. However, if this step is executed, then the XRT79L71 will generate an interrupt to the
Microprocessor anytime the Receive LAPD Controller block has completed its reception of a new PMDL
Message. The purpose of this interrupt is to notify the Microprocessor that the Receive LAPD Message buffer
contains a newly received LAPD/PMDL Message that needs to be read.
The procedure for enabling the Receive LAPD Interrupt is actually a three-step process.
STEP 4a - Enable the DS3/E3 Framer block interrupts - At the Operational Block Level.
This step is accomplished by setting Bit 2 (DS3/E3 Framer Block Interrupt Enable) to "1" as illustrated below.
This step enables the DS3/E3 Framer block for interrupt generation at the Operational Block Level.
STEP 4b - Enable the Receive DS3/E3 Framer block Interrupts - At the Block Level.
This step is accomplished by setting Bit 7 (Receive DS3/E3 Framer Block Interrupt Enable), within the Block
Interrupt Enable Register, to "1", as illustrated below.
Receive DS3 LAPD Status Register (Address = 0x1119)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
RxABORT
RxLAPDType[1:0]
RxCR Type
RxFCS Error
End of
Message
Flag Present
R/O
0
1
Operation Block Interrupt Enable Register - Byte 1 (Address = 0x0116)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
DS3/E3
LIU/JA Block
Interrupt
Enable
DS3/E3
Framer
Block Inter-
rupt Enable
Unused
R/O
R/W
R/O
0
1
0