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PRELIMINARY
XRT79L71
222
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
Therefore, if a given DS3 Terminal Equipment receives a DS3 signal, in which the AIC bit is set to "0", then the
Terminal Equipment can definitely conclude that it is receiving a DS3 signal that is of the M13/M23 Framing
format. However, if a given DS3 Terminal Equipment receives a DS3 signal in which the AIC bit is always set
to "1" then the Terminal Equipment can largely assume, but not definitely conclude that it is receiving a DS3
signal that is of the C-bit Parity Framing format.
Determining the value of the AIC Bit, within a given DS3 data-stream
The user can determine the value of the AIC bit, within a given incoming DS3 data-stream by reading out the
state of Bit 3 (RxAIC) within the Receive DS3 Status Register, as depicted below.
If RxAIC is set to "0" then the user can conclude that the Receive DS3 Framer block is currently receiving a
DS3 signal that is of the M13/M23 Framing format. Conversely, if RxAIC is set to "1", then the user can
conclude that the Receive DS3 Framer block is mostly likely receiving a DS3 signal that is of the C-bit Parity
Framing format.
Tracking Changes within the AIC Bit
If the Receive DS3 Framer block were to suddenly receive a DS3 data-stream that now has a different AIC
value, and if this change in AIC value persists for at least two DS3 frame periods, then the following will
happen.
The Receive DS3 Framer block will update the contents of Bit 3 (RxAIC) within the Receive DS3 Status
Register.
The Receive DS3 Framer block will generate the Change of AIC State Interrupt. The Receive DS3 Framer
block will indicate that it is generating this interrupt by asserting the Interrupt Request output pin by toggling
it "Low" and by setting Bit 2 (Change of AIC State Interrupt Status) within the Receive DS3 Interrupt Status
Register, to "1" as depicted below.
Receive DS3 Status Register (Address = 0x1111)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
FERF Defect
Declared
RxAIC
RxFEBE[2:0]
R/O
0
X
0
Receive DS3 Status Register (Address = 0x1111)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
FERF Defect
Declared
RxAIC
RxFEBE[2:0]
R/O
0
X
0