
XRT79L71
PRELIMINARY
131
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
Once the user executes this step, then the Transmit LAPD Controller will proceed to do the following.
a. It will parse through the contents of the Transmit LAPD Message buffer and will zero-stuff the payload
portion of the outbound PMDL Message.
b. It will compute and append the Frame Check Sequence (FCS) value, to the back end of the outbound
PMDL Message.
c. It will begin in a bit-by-bit manner inserting the resulting PMDL Message into the DL bit-fields, within the
outbound DS3 frames.
NOTES:
1.
After the user has set the Initiate Transmission of LAPD/PMDL Message bit to "1", the user is advised some time
later to execute another write operation to this register that sets the Initiate Transmission of LAPD/PMDL Message
bit to "0".
2.
Once the Transmit LAPD Controller has started to transmit the PMDL Message to the remote terminal, it will
denote this by setting the Transmit LAPD Controller Busy bit-field within the Transmit DS3 LAPD Status/Interrupt
register to "1", as illustrated below.
This bit-field permits the user to poll the status of the Transmit LAPD Controller. Once the Transmit LAPD
Controller has completed the transmission of the LAPD Message frame, this bit-field will toggle back to "0".
Transmit DS3 LAPD Status/Interrupt Register (Address = 0x1134)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Initiate
Transmission
of LAPD/
PMDL Mes-
sage
Transmit LAPD
Controller Busy
Transmit LAPD
Interrupt
Enable
Transmit LAPD
Interrupt Status
RO
R/W
RO
R/W
RUR
0
0->1
0
1
0
Transmit DS3 LAPD Status/Interrupt Register (Address = 0x1134)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Initiate
Transmission
of LAPD/
PMDL Mes-
sage
Transmit LAPD
Controller Busy
Transmit LAPD
Interrupt
Enable
Transmit LAPD
Interrupt Status
RO
R/W
RO
R/W
RUR
0
1
0