xr
PRELIMINARY
XRT86VL38
REV. P1.0.6
OCTAL T1/E1/J1 FRAMER/LIU COMBO
300
3.6
The Interrupt Structure within the Framer
The XRT86VL38 Framer is equipped with a sophisticated Interrupt Servicing Structure. This Interrupt Structure includes an
Interrupt Request output pin INT, numerous Interrupt Enable Registers and numerous Interrupt Status Registers.
The Interrupt Servicing Structure, within the XRT86VL38 Framer contains three levels of hierarchy:
•
The Framer Level
•
The Block Level
•
The Source Level.
The Framer Interrupt Structure has been carefully designed to allow the user to quickly determine the exact source of this
interrupt (with minimal latency) which will aid the microprocessor in determining the which interrupt service routine to call up
in order to eliminate or properly respond to the condition(s) causing the interrupt.
The XRT86VL38 Framer comes equipped with registers to support the servicing of this wide array of potential “interrupt re-
quest” sources. Table 178 lists the possible conditions that can generate interrupts.
General Flow of Interrupt Servicing
When any of the conditions presented in Table 178 occur, (if their Interrupt is enabled), then the Framer generates an inter-
rupt request to the microprocessor by asserting the active-low interrupt request output pin, INT. Shortly after the local micro-
processor has detected the activated INT signal, it will enter into the appropriate user-supplied interrupt service routine.
The first task for the microprocessor, while running this interrupt service routine, may be to isolate the source of the inter-
rupt request down to the device level (e.g, the Framer IC), if multiple peripheral ICs exist in the user's system. However,
once the interrupting peripheral device has been identified, the next task for the microprocessor is to determine exactly
what feature of functional section within the device requested the interrupt.
T
ABLE
178: L
IST
OF
THE
P
OSSIBLE
C
ONDITIONS
THAT
CAN
G
ENERATE
I
NTERRUPTS
,
IN
EACH
F
RAMER
I
NTERRUPT
B
LOCK
I
NTERRUPTING
C
ONDITION
Framer Level
Loss of RxLineClk Signal· One Second Interrupt
HDLC Controller Block
Transmit HDLC - Start of Transmission
Receive HDLC - Start of Reception
Transmit HDLC - End of Transmission
Receive HDLC - End of Reception
FCS Error
Receipt of Abort Sequence
Receipt of Idle Sequence
Slip Buffer Block
Slip Buffer Full
Slip Buffer Empty
Slip Buffer - Slip
Alarm & Error Block
Receipt of CAS Multi-frame Yellow Alarm
Detection of Loss of Signal Condition
Detection of Line Code Violation
Change in Receive Loss of Framer Condition
Change in Receive AIS Condition
Receipt of FAS Frame Yellow Alarm
T1/E1 Frame Block
Change in CAS Multi-Frame Alignment
Change in National Bits· Change in CAS Signaling Bits
Change in FAS Frame Alignment· Change in the "In Frame" Condition
Detection of "Frame Mimicking Data"
Detection of Sync (CRC-4/CRC-6) Errors
Detection of Framing Bit Errors