XRT72L58 Datasheet, PDF (318/486 Pages) Exar Corporation – EIGHT CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L58
EIGHT CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
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PRELIMINARY
FIGURE 126. WAVEFORM/TIMING RELATIONSHIP BETWEEN TXLINECLK, TXPOS AND TXNEG - TXPOS AND
TXNEG ARE CONFIGURED TO BE UPDATED ON THE FALLING EDGE OF TXLINECLK
t32
TxLineClk
t31
t33
TxPOS
TxNEG
5.2.6 Transmit Section Interrupt Processing
The Transmit Section of the XRT72L58 can generate
an interrupt to the Microprocessor/Microcontroller for
the following reasons.
• Completion of Transmission of LAPD Message
5.2.6.1 Enabling Transmit Section Interrupts
The Interrupt Structure, within the XRT72L58 con-
tains two hierarchical levels:
• Block Level
• Source Level
The Block Level
The Enable State of the Block Level for the Transmit
Section Interrupts dictates whether or not interrupts
(enabled) at the source level, are actually enabled.
The user can enable or disable these Transmit Sec-
tion interrupts, at the Block Level by writing the appro-
priate data into Bit 1 (Tx DS3/E3 Interrupt Enable)
within the Block Interrupt Enable register (Address =
0x04), as illustrated below.
BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxDS3/E3
Interrupt
Enable
Not Used
TxDS3/E3
Interrupt
Enable
One-Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables the Transmit Sec-
tion (at the Block Level) for Interrupt Generation.
Conversely, setting this bit-field to “0” disables the
Transmit Section for interrupt generation.
What does it mean for the Transmit Section Inter-
rupts to be enabled or disabled at the Block Lev-
el?
If the Transmit Section is disabled (for interrupt gener-
ation) at the Block Level, then ALL Transmit Section
interrupts are disabled, independent of the interrupt
enable/disable state of the source level interrupts.
If the Transmit Section is enabled (for interrupt gener-
ation) at the block level, then a given interrupt will be
enabled at the source level. Conversely, if the Trans-
mit Section is enabled (for interrupt generation) at the
Block level, then a given interrupt will still be disabled,
if it is disabled at the source level.
As mentioned earlier, the Transmit Section of the
XRT72L58 Framer IC contains the Completion of
Transmission of LAPD Message Interrupt.
The Enabling/Disabling and Servicing of this interrupt
is presented below.
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