
á
á THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER XRT72L53
PRELIMINARY
REV. P1.1.7
136
Once the Microprocessor/Microcontroller has read
the register that corresponds to the interrupting
source within the Framer, the following things will
happen.
1. The Asserted Interrupt Status bit-fields within this
register will be reset upon read.
2. The Asserted bit-field, within the Block Interrupt
Status register will be reset.
3. The Framer device will negate the INT (Interrupt
Request) output pin, by driving this output pin
"High”.
2.7.1
Automatic Reset of Interrupt Enable Bits
Occasionally, the user’s system (which includes the
Framer) may experience a fault condition, such that a
Framer Interrupt Condition will continuously exist. If
this particular interrupt condition has been enabled
(within the Framer IC) then the Framer will generate
an interrupt request to the MIcroprocessor/Microcon-
troller. Afterwards, the Microprocessor/Microcontroller
will attempt to service this interrupt by reading the
Block Interrupt Status register and the subsequent
source level interrupt status registers. Additionally,
the Microprocessor/Microcontroller will attempt to
perform some system-related tasks in order to try to
resolve those conditions causing the interrupt. After
the Microprocessor/Microcontroller has attempted all
of these things, the Framer IC will negate the INT out-
put pin. However, because the system fault still re-
mains, the conditions causing the Framer to issue this
interrupt request, also still exists. Consequently, the
Framer will generate another interrupt request, which
forces the Microprocessor/Microcontroller to once
again attempt to service this interrupt. This phenome-
TABLE 10: INTERRUPT SERVICE ROUTINE GUIDE (FOR DS3 APPLICATIONS)
INTERRUPTING
FUNCTIONAL BLOCK
THE NEXT REGISTERS TO BE READ DURING THE INTERRUPT SERVICE
ROUTINE
REGISTER ADDRESS
Receive Section
RxDS3 Interrupt Status Register
0 x 013
RxDS3 FEAC Interrupt Enable/Status Register
0 x 17
RxDS3 LAPD Control Register
0 x 18
Transmit Section
TxDS3 FEAC Configuration and Status Register
0 x 31
TxDS3 LAPD Status/Interrupt Register
0 x 34
TABLE 11: INTERRUPT SERVICE ROUTINE GUIDE (FOR E3, ITU-T G.832 APPLICATIONS)
INTERRUPTING
FUNCTIONAL BLOCK
THE NEXT REGISTERS TO BE READ DURING THE INTERRUPT SERVICE
ROUTINE
REGISTER ADDRESS
Receive Section
RxE3 Interrupt Status Register - 1
0 x 014
RxE3 Interrupt Status Register - 2
0 x 15
RxE3 LAPD Control Register
0 x 18
Transmit Section
TxE3 LAPD Status and Interrupt Register
0 x 34
TABLE 12: INTERRUPT SERVICE ROUTINE GUIDE (FOR E3, ITU-T G.751 APPLICATIONS)
INTERRUPTING
FUNCTIONAL BLOCK
THE NEXT REGISTERS TO BE READ DURING THE INTERRUPT SERVICE
ROUTINE
REGISTER ADDRESS
Receive Section
RxE3 Interrupt Status Register - 1
0 x 014
RxE3 Interrupt Status Register - 2
0 x 15
RxE3 LAPD Control Register
0 x 18
Transmit Section
TxE3 LAPD Status and Interrupt Register
0 x 34