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PRELIMINARY
XRT79L71
126
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
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 back 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 then toggle back to
"0".
The Procedure for Transmitting a standard LAPD/PMDL Message presented in a Flow-Chart
the user should use in order to transmit a PMDL Message via the Transmit LAPD Controller, when the Transmit
LAPD Controller is configured to retransmit the LAPD Message frame, repeatedly at one-second intervals.
This figure also indicates via the shaded boxes what the Transmit LAPD Controller circuitry will do before and
during message transmission.
Figure 54 presents the procedure in white boxes that the user should use in order to transmit a PMDL
Message via the Transmit LAPD Controller, when the Transmit LAPD Controller is configured to transmit the
LAPD Message frame only once, and then halt transmission.
4.2.4.2
Transmitting Non-Standard Variable Length (e.g., up to 82 bytes) LAPD Messages
The user can (1) write the contents of the outbound PMDL Message into the Transmit LAPD Message buffer
and (2) command the Transmit LAPD Controller to begin the transmission of this PMDL Message by executing
the following steps.
STEP 1 - Make sure that the XRT79L71 has been configured to operate in the C-Bit Parity Framing
format.
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 Inter-
rupt Enable
Transmit
LAPD Inter-
rupt Status
RO
R/W
RO
R/W
RUR
0
1
0
Figure 54. Flow Chart depicting how to use the Transmit LAPD Controller when the Transmit LAPD
Controller is configured to re-transmit the LAPD Message frames repeatedly at one-second intervals
Figure 55. Flow Chart depicting how to use the Transmit LAPD Controller when the Transmit LAPD
Controller is configured to re-transmit the LAPD Message frames repeatedly at one-second intervals