Description: The S/UNI-JET supports both M23 and C-bit parity DS3 framing formats. This format can be extended to support direct byte map- -ping or PLCP mapping of ATM cells.

Adm ---- M23 Operation: The C bits are passed through transparently in M23 framer only mode except for the C-bit Parity ID bit which toggles every M fra- -me. In M23 ATM applications, the C bits other than the Parity ID bit are forced to logic one.

Plcp ---- C-bit Parity Operation: The C-bit Parity ID bit is forced to logic one. The second C-bit in Msubframe 1 is set to logic one. The third C-bit in M-subframe 1 provides a far-end alarm and control (FEAC) signal. The FEAC channel is sourced by the XBOC block. The 3 C-bits in Msubframe 3 carry path parity information. The value of these 3 C-bits is the same as that of the P-bits. The 3 C-bits in Msubframe 4 are the FEBE bits. The 3 C-bits in M-subframe 5 contain the 28.2 Kbit/s path maintenance datalink. The remaining C-bits are unused and set to logic one.