
XRT72L50
á
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
275
LAPD Transmitter to transmit a corrupted message to the Remote Terminal Equipment. 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 Framer to automatically reset activated interrupts.
The user can do this by writing a “1” into Bit 3 within the Framer Operating Mode register (Address = 0x00), as
depicted below.
This action will prevent the LAPD Transmitter from generating its own One-Second interrupt (following each
transmission of the LAPD Message frame).
2. Enable the One-Second Interrupt
This can be done by writing a “1” into Bit 0 (One-Second Interrupt Enable) within the Block Interrupt Enable
Register, as depicted below.
3. Write the new message into the Transmit LAPD Message buffer immediately after the occurrence of the
One-Second Interrupt
By synchronizing the writes to the Transmit LAPD Message buffer to occur immediately after the occurrence of
the One-Second Interrupt, the user avoids conflicting with the One-Second transmission of the LAPD Message
frame, and will transmit the correct (uncorrupted) PMDL Message to the Remote LAPD Receiver.
5.2.4
The Transmit E3 Framer Block
5.2.4.1
Brief Description of the Transmit E3 Framer
The Transmit E3 Framer block accepts data from any of the following four sources, and uses it to form the E3
data stream.
The Transmit Payload Data Input block
The Transmit Overhead Data Input block
The Transmit HDLC Controller block
The Internal Overhead Data Generator
The manner in how the Transmit E3 Framer block handles data from each of these sources is described below.
Framer Operating Mode Register (Address = 0x00)
BIT 7BIT 6BIT 5BIT 4
BIT 3BIT 2BIT 1BIT 0
Local Loop-back
DS3/E3
Internal
LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
TimRefSel[1:0]
R/W
00
1
0
10
1
Block Interrupt Enable Register (Address = 0x04)
BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1
BIT 0
RxDS3/E3
Interrupt
Enable
Not Used
TxDS3/E3
Interrupt
Enable
One-Second
Interrupt
Enable
R/W
RORO
RO
RORO
R/W
00
000
00
1