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XRT79L71
PRELIMINARY
545
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
NOTE: Since we are discussing the "Change in SSM" Interrupt, Bit 6 (Change in SSM Message Interrupt Status), within the
"Receive E3 Interrupt Status Register # 1 - G.832" has been set to "1" as depicted above.
STEP 4 - At a minimum, the user should read out the contents of the new SSM.
This is accomplished by reading out Bits 3 through 0 (RxSSM[3:0]) within the "Receive E3 SSM Register -
G.832" as depicted below.
NOTE: The user will likely have some additional (system-related) task that must be performed in response to the "Change
in SSM" Interrupt.
6.3.4.4.2
THE SSM OUT-OF-SEQUENCE INTERRUPT
As mentioned earlier, whenever a "transmitting" E3 terminal transmits the SSM to the remote terminal
equipment, it does so by repeatedly transmitting this four-bit SSM message, one bit at a time (or one bit per E3
frame period) via Bit 8 (the least significant bit-field) within the MA byte. As this "Transmitting" E3 Terminal
repeatedly transmits this byte (to the remote terminal equipment) it will use Bits 6 and 7 (within the MA byte) to
indicate which SSM Message bit is being transported via Bit 8, within the current MA byte. Depending upon
which of the four bits (within the SSM) that is being transported via the MA byte, within a given E3 frame, the
"Transmitting" E3 Terminal will set Bits 6 anid 7 to the appropriate value, in order to "identify" this SSM bit, as
Receive E3 Interrupt Status Register # 2 - G.832 (Address = 0x1115)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Change in
Receive
Trail-Trace
Message
Interrupt
Status
Reserved
Detection of
FEBE/REI
Event
Interrupt
Status
Change in
FERF/RDI
Defect
Condition
Interrupt
Status
Detection of
BIP-8 Error
Interrupt
Status
Detection of
Framing
Byte Error
Interrupt
Status
RxPLD
Mismatch
Interrup
Status
R/O
RUR
R/O
RUR
0
Receive E3 SSM Register - G.832 (Address = 0x112C)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxSSM
Enable
MF[1:0]
Reserved
RxSSM[3:0]
R/W
R/O
1
X
0
X
TABLE 68: THE RELATIONSHIP BETWEEN THE STATES OF BITS 6 AND 7 (WITHIN THE MA BYTE) AND THE EXACT
SSM BIT THAT IS BEING TRANSPORTED VIA BIT 8, WITHIN THE CURRENT MA BYTE
MA BYTE, BIT 6
MA BYTE, BIT 7
THE SSM BIT BEING TRANSPORTED IN BIT 8
0
SSM Bit 1 (The MSB)
0
1
SSM Bit 2
1
0
SSM Bit 3
1
SSM Bit 4 (The LSB)