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PRELIMINARY
XRT79L71
120
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
STEP 2 - Enable the Transmit LAPD Controller
This is accomplished by setting Bit 0 (Transmit LAPD Enable) within the Transmit DS3 LAPD Configuration
Register to "1", as illustrated below.
NOTES:
1.
For normal operation, it is imperative that the user also make sure that bit 4 (Reserved) and bit 7 (Transmit LAPD
Any) within this register are both set to "0".
2.
Once the user executes the above mentioned step, then the Transmit LAPD Controller will begin to transmit the
Idle (Flag) Sequence (e.g., a continuous, repeating string of octets, of the value 0x7E) via the DL bits within each
outbound DS3 frame.
STEP 3 - Configure the Transmit LAPD Controller to Auto-Retransmit (Optional)
In some applications, it may be desirable to configure the Transmit LAPD Controller to repeatedly transmit a
LAPD/PMDL Message at one-second intervals. To configure the Transmit LAPD Controller block to do this,
then the user should write a "1" into Bit 3 (Auto Retransmit) within the Transmit DS3 LAPD Configuration
Register. This action is depicted below.
STEP 4 - Specify the type of LAPD Message to be transmitted.
At this stage it is necessary to specify the type of LAPD Message that is to be transmitted. The Transmit and
Receive LAPD Controller blocks, within the XRT79L71 are capable of supporting the following standard types
of LAPD Messages.
Framer Operating Mode Register (Address = 0x1100)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Local
Loop-back
DS3/E3*
Internal
LOS
Enable
RESET
Direct Mapped
ATM
Frame Format
Timing Reference
Select [1:0]
R/W
X
1
X
0
X
0
X
Transmit DS3 LAPD Configuration Register (Address = 0x1133)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Transmit
LAPD Any
Unused
Auto Retransmit
Unused
Tx LAPD
Msg
Length
Transmit
LAPD
Enable
R/W
RO
R/O
R/W
R/O
R/W
0
X
1
Transmit DS3 LAPD Configuration Register (Address = 0x1133)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LAPD Any
Unused
Auto
Retransmit
Unused
Transmit
LAPD
Message
Length
Transmit
LAPD
Enable
R/W
RO
R/O
R/W
R/O
R/W
0
1
0
X
1