DS3173N datasheet(86/232 Pages) DALLAS

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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. P1, P2, C31, C32, and C33 are overwritten with the calculated payload parity from the previous

output DS3 frame. And, CX1, CX2, and CX3 (X

¹ 3) are overwritten with 000. AIS will overwrite a transmit Idle signal.

10.6.5.5.1 Receive C-bit DS3 Frame Format

The DS3 frame format is shown in Figure 10-14. X1 and X2 are the Remote Defect Indication (RDI) bits (also

referred to as the far-end SEF/AIS bits). P1 and P2 are the parity bits used for line error monitoring. M1, M2, and M3

are the multiframe alignment bits that define the multiframe boundary. FXY are the subframe alignment bits that

define the subframe boundary. Note: Both the M-bits and F-bits define the DS3 frame boundary. C11 is the

Application Identification Channel (AIC). C12 is reserved for future network use, and has a value of one. C13 is the

Far-End Alarm and Control (FEAC) signal. C21, C22, and C23 are unused, and have a value of one. C31, C32, and C33

are the C-bit parity bits used for path error monitoring. C41, C42, and C43 are the Far-End Block Error (FEBE) bits

used for remote path error monitoring. C51, C52, and C53 are the path maintenance data link (or HDLC) bits. C61,

C62, and C63 are unused, and have a value of one. C71, C72, and C73 are unused, and have a value of one.

10.6.5.5.2 Receive C-bit DS3 Overhead Extraction

Overhead extraction extracts all of the DS3 overhead bits from the C-bit DS3 frame. All of the DS3 overhead bits

X1, X2, P1, P2, MX, FXY, and CXY are output on the receive overhead interface (ROH, ROHSOF, and ROHCLK). The

P1, P2, C31, C32, and C33 bits are output as an error indication (modulo 2 addition of the calculated parity and the

bit). The C13 bit is sent over to the receive FEAC controller. The C51, C52, and C53 bits are sent to the receive HDLC

overhead controller.

10.6.6 M23 DS3 Framer/Formatter

10.6.6.1 Transmit M23 DS3 Frame Processor

The M23 DS3 frame format is shown in Figure 10-14. Table 10-28 defines the framing bits for M23 DS3. X1 and X2

are the Remote Defect Indication (RDI) bits (also referred to as the far-end SEF/AIS bits). P1 and P2 are the parity

bits used for line error monitoring. M1, M2, and M3 are the multiframe alignment bits. FXY are the subframe

alignment bits. C11 is the Application Identification Channel (AIC). CX1, CX2, and CX3 are the stuff control bits for

tributary #X. The X-bit, P-bit, M-bit, C-bit, and F-bit positions are overhead bits, and the remainder of the bit

positions in the T3 frame are payload bits regardless of how they are marked by TDEN.

Table 10-28. 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

10.6.6.2 Transmit M23 DS3 Frame Generation

M23 DS3 frame generation receives the incoming payload data stream, and overwrites all of the DS3 overhead bit

locations.

The multiframe alignment bits (M1, M2, and M3) are overwritten with the values zero, one, and zero (010)

respectively.

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