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XRT79L71
PRELIMINARY
487
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
NOTES:
1.
After the user has set the Initiate Transmission of LAPD/PMDL Message bit to "1", the user is advised to (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 E3 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".
The Mechanics of Transmitting a New LAPD Message, if the Transmit LAPD Controller has been
configured to retransmit the LAPD Message frame, repeatedly at one-second intervals
If the Transmit LAPD Controller has been configured to retransmit the LAPD Message repeatedly at one-
second intervals, then it will do the following at one-second intervals.
Parse through the contents of the Transmit LAPD Message buffer and Zero-Stuff the PMDL Message
Read in the stuffed PMDL Message from the Transmit LAPD Message buffer
Encapsulate this stuffed PMDL Message into a LAPD Message frame
Transmit this LAPD Message frame to the Remote Terminal.
To transmit another (e.g., different) PMDL message to the remote Receive LAPD Controller, the user will have
to write this new message into the Transmit LAPD Message buffer, via the Microprocessor Interface section of
the channel. However, the user must be careful when writing in this new message. If the user writes this
message into the Transmit LAPD Message buffer at the wrong time with respect to these one-second LAPD
Message frame transmissions, the user's action could interfere with these transmissions thereby causing the
Transmit LAPD Controller to transmit a corrupted message to the remote Receive LAPD Controller. In order to
avoid this problem, while writing the new message into the Transmit LAPD Message buffer, the user should do
the following:
1.
Configure the DS3/E3 Framer Block to automatically reset activated interrupts
The user can do this by writing a "1" into Bit 1 (Enable Interrupt Auto-Clear) within the Operating Mode
Register, as depicted below.
Transmit E3 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
Operation Control Register - Byte 2 (Address = 0x0101)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Interrupt
WC/INT*
Enable
Interrupt
Auto-Clear
Interrupt
Enable
R/O
R/W
0
1
0