DS3172 datasheet(83/232 Pages) DALLAS

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P-bit parity errors are determined by calculating the parity of the current DS3 frame (payload bits only), and

comparing the calculated parity to the P-bits (P1 and P2) in the next DS3 frame. If the calculated parity does not

match P1 or P2, a single P-bit parity error is declared.

C-bit parity errors (C-bit format only) are determined by calculating the parity of the current DS3 frame (payload bits

only), and comparing the calculated parity to the C-bits in subframe three (C31, C32, and C33) in the next DS3 frame.

If the calculated parity does not match C31, C32, or C33, a single C-bit parity error is declared.

FEBE errors (C-bit format only) are determined by the C-bits in subframe four (C41, C42, and C43). A value of 111

indicates no error and any other value indicates an error.

The receive alarm indication (RAI) bit will be set high in the transmitter when one or more of the indicated alarm

conditions is present, and low when all of the indicated alarm conditions are absent. Setting the receive alarm

indication on LOS, SEF, LOF, or AIS is individually programmable (on or off).

The Application Identification Channel (AIC) is stored in a register bit. It is determined from the C11 bit. The AIC is

set to one (C-bit format) if the C11 bit is set to one in thirty-one consecutive multiframes. The AIC is set to zero (M23

format) if the C11 bit is set to zero in four of the last thirty-one consecutive multiframes. Note: The stored AIC bit

must not change when an LOS, OOF, or AIS condition is present.

A FEBE is transmitted by default upon reception of a DS3 frame in which a C-bit parity error or a framing error is

detected and counted.

10.6.5 C-bit DS3 Framer/Formatter

10.6.5.1 Transmit C-bit DS3 Frame Processor

The C-bit DS3 frame format is shown in Figure 10-14.

Figure 10-14. DS3 Frame Format

680 Bits

7 Sub-

Frames

Table 10-27 shows the function of each overhead bit in the DS3 Frame.

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