
XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
230
The purpose of generating an interrupt to the local
μP upon “FEAC Code Word Validation” is to inform
the local μP that the UNI has a “newly received”
FEAC message that needs to be read. The local μP
would read-in this FEAC code word from the Rx DS3
FEAC Register (Address = 12h).
FEAC Code Removal
After the 10th transmission of a given FEAC code
word, the “Far-End” Transmit DS3 Framer may start
to transmit a different FEAC code word. When the
Receive FEAC processor detects this occurrence, it
must “Remove” the FEAC codeword that is presently
residing in the Rx DS3 FEAC Register. The Receive
FEAC Processor will “remove” the existing FEAC
code word when it detects that 3 (or more) out of the
last 10 received FEAC codes are different from the
latest “validated” FEAC code word. The Receive
FEAC Processor will inform the local μP/μC of this
“removal” event by generating a “Rx FEAC Removal”
interrupt, and asserting the “RxFEAC Remove Inter-
rupt Status” bit in the Rx DS3 Interrupt Enable/Status
Register, as depicted below.
Additionally, the Receive FEAC processor will also
denote the “removal” event by setting the “FEAC Valid”
bit-field (Bit 4), within the Rx DS3 FEAC Interrupt
Enable/Status Register to “0”, as depicted above.
The description of Bits 0 through 3 within this register,
all support Interrupt Processing, and will therefore be
presented in Section 7.1.2.9. Figure 69 presents a
flow diagram depicting how the Receive FEAC
Processor functions.
Rx DS3 FEAC Register (Address = 12h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Unused
RxFEAC [5]
RxFEAC [4]
RxFEAC [3]
RxFEAC [2]
RxFEAC [1]
RxFEAC [0]
Unused
R/O
R/O
R/O
R/O
R/O
R/O
R/O
R/O
Rx DS3 FEAC Interrupt Enable/Status Register (Address = 13h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Unused
Unused
Unused
FEAC
Valid
RxFEAC
Remove
Interrupt Enable
RxFEAC
Remove
Interrupt Status
RxFEAC Valid
Interrupt Enable
RxFEAC Valid
Interrupt Status
R/O
R/O
R/O
R/O
R/W
RUR
R/W
RUR
x
x
x
0
x
1
x
0