DS3181/DS3182/DS3183/DS3184
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The bit C13 is overwritten with the Far-End Alarm and Control (FEAC) data input from the transmit FEAC controller.
The bits C31, C32, and C33 are all overwritten with the calculated payload parity from the previous DS3 frame.
The bits C41, C42, and C43 are all overwritten with the Far-End Block Error (FEBE) bit. The FEBE bit can be
generated automatically or inserted from a register bit. The FEBE bit source is programmable (automatic or
register). If the T3.TCR.AFEBED register bit is one then the T3.TCR.TFEBE register bit controls this bit. If the
FEBE bit is generated automatically, it is zero when at least one C-bit parity error has been detected during the
previous frame.
The bits C51, C52, and C53 are overwritten with the path maintenance data link input from the HDLC controller.
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 to error insertion. Frame generation is programmable
(on or off). Note: P-bit generation may still be performed even if frame generation is disabled.
10.10.5.3 Transmit C-bit 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, P-bit parity errors, C-bit parity errors, and Far-End Block Error (FEBE) errors.
The framing error insertion mode is programmable (F-bit, M-bit, SEF, or OOMF). An F-bit error is a single sub-
frame 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 sub-frame alignment bits in a sub-frame (FX1, FX2, FX3, and FX4). An OOMF error is a
single multiframe alignment bit (M1, M2, or M3) error in 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.
A C-bit parity error is generated by is inverting the value of the C31, C32, and C33 bits in a single DS3 frame. C-bit
parity error(s) can be inserted one error at a time, or continuously. The C-bit parity error insertion mode (single or
continuous) is programmable.
A FEBE error is generated by forcing the C41, C42, and C43 bits in a single multiframe to zero. FEBE error(s) can be
inserted one error at a time, or continuously. The FEBE error insertion rate (single or continuous) is programmable.
Each error type (framing, P-bit parity, C-bit parity, or FEBE) has a separate enable. Continuous error insertion
mode inserts errors at every opportunity. Single error insertion mode inserts an error at the next opportunity when
requested. The framing multi-error modes (SEF or OOMF) insert the indicated number of error(s) at the next
opportunities when requested; i.e., a single request will cause multiple errors to be inserted. The requests can be
initiated by a register bit (TSEI) or by the manual error insertion input (TMEI). The error insertion initiation type
(register or input) is programmable. The insertion of each particular error type is individually enabled. Once all error
insertion has been performed, the data stream is passed on to overhead insertion.
10.10.5.4 Transmit C-bit DS3 Overhead Insertion
Overhead insertion can insert any (or all) of the DS3 overhead bits into the DS3 frame. The DS3 overhead bits X1,
X2, P1, P2, MX, FXY, and CXY can be sourced from the transmit overhead interface (TOHCLKn, TOHn, TOHENn, and
TOHSOFn). The P-bits (P1 and P2) and C31, C32, and C33 bits are received as an error mask (modulo 2 addition of
the input bit and the internally generated bit). The DS3 overhead insertion is fully controlled by the transmit
overhead interface. If the transmit overhead data enable signal (TOHENn) is driven high, then the bit on the
transmit overhead signal (TOHn) is inserted into the output data stream. Insertion of bits using the TOHn signal
overwrites internal overhead insertion.
10.10.5.5 Transmit C-bit DS3 AIS/Idle Generation
C-bit DS3 AIS/Idle generation overwrites the data stream with AIS or an Idle signal. If transmit Idle is enabled, the
data stream payload is forced to an 1100 pattern with two ones immediately following each DS3 overhead bit. M1,
M2, and M3 bits are overwritten with the values zero, one, and zero (010) respectively. FX1, FX2, FX3, and FX4 bits are
overwritten with the values one, zero, zero, and one (1001) respectively. X1 and X2 are overwritten with 11. And,
P1, P2, C31, C32, and C33 are overwritten with the calculated payload parity from the previous output DS3 frame.
If transmit AIS is enabled, the data stream payload is forced to a 1010 pattern with a one immediately following
each DS3 overhead bit. M1, M2, and M3 bits are overwritten with the values zero, one, and zero (010) respectively.
FX1, FX2, FX3, and FX4 bits are overwritten with the values one, zero, zero, and one (1001) respectively. X1 and X2