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DS3161/DS3162/DS3163/DS3164
Table 10-33. M23 DS3 Frame Overhead Bit Definitions
Bit
Definition
X1, X2
Remote Defect Indication
(RDI)
P1, P2
Parity Bits
M1, M2, and M3
Multiframe Alignment Bits
FXY
Subframe Alignment Bits
C11
Application Identification
Channel (AIC)
CX1, CX2, and CX3
Stuff Control Bits for Tributary
#X
10.10.6.2 Transmit M23 DS3 Frame Generation
M23 DS3 frame generation receives the incoming payload data stream, and overwrites the entire DS3 overhead bit
locations.
The multiframe alignment bits (M1, M2, and M3) are overwritten with the values zero, one, and zero (010)
respectively.
The subframe alignment bits (FX1, FX2, FX3, and FX4) are overwritten with the values one, zero, zero, and one (1001)
respectively.
The X-bits (X1 and X2) are both overwritten with the Remote Defect Indicator (RDI). The RDI source is
programmable (automatic, 1, or 0). If the T3.TCR.ARDID is one then the T3.TCR.TRDI register bit controls this bit.
If the RDI is generated automatically (T3.TCR.ARDID=0), the X-bits are set to zero when one or more of the
indicated alarm conditions is present, and set to one when all of the indicated alarm conditions are absent.
Automatically setting RDI on LOS, SEF, LOF, or AIS is individually programmable (on or off).
The P-bits (P1 and P2) are both overwritten with the calculated payload parity from the previous DS3 frame. The
payload parity is calculated by performing modulo 2 addition of all of the payload bits after all frame processing has
been completed. P-bit generation is programmable (on or off). The P-bits will be generated if either P-bit generation
is enabled or frame generation is enabled.
If C-bit generation is enabled (T3.TCR.CBGE), the bit C11 is overwritten with an alternating one zero pattern, and all
of the other C-bits (CXY) are overwritten with zeros. If C-bit generation is disabled, then all of the C-bit timeslots
(CXY) will be treated as payload data, and passed through. C-bit generation is programmable (on or off). Note:
Overhead insertion may still overwrite the C-bit time slots even if C-bit generation is disabled.
Once all of the DS3 overhead bits have been overwritten, the data stream is passed on to error insertion. If frame
generation is disabled, the incoming DS3 signal is passed on directly to error insertion. Frame generation is
programmable (on or off). Note: P-bit generation may still be performed even if frame generation is disabled.
10.10.6.3 Transmit M23 DS3 Error Insertion
Error insertion inserts various types of errors into the different DS3 overhead bits. The types of errors that can be
inserted are framing errors and P-bit parity errors.
The framing error insertion mode is programmable (F-bit, M-bit, SEF, or OOMF). An F-bit error is a single subframe
alignment bit (FXY) error. An M-bit error is a single multiframe alignment bit (M1, M2, or M3) error. An SEF error is an
error in all the subframe alignment bits in a subframe (FX1, FX2, FX3, and FX4). An OOMF error is a single multiframe
alignment bit (M1, M2, or M3) error in each of two consecutive DS3 frames.
A P-bit parity error is generated by is inverting the value of the P-bits (P1 and P2) in a single DS3 frame. P-bit parity
error(s) can be inserted one error at a time, or continuously. The P-bit parity error insertion mode (single or
continuous) is programmable.