Bt8370/8375/8376
2.0 Circuit Description
2.4 Receiver
Fully Integrated T1/E1 Framer and Line Interface
2.4.7 Receive Framing
Two framers are in the receive data stream: an offline framer and an online frame
status monitor. The offline framer recovers receive frame alignment; the online
framer monitors frame alignment patterns and recovers multiframe alignment in
E1 modes. Frame and multiframe synchronization criteria used by the framers
and monitoring criteria of the online framer are selected in RFRAME[3:0] of the
Primary Control register [CR0; addr 001].
Receive frame synchronization is initiated by the online framer’s activation of
the Receive Loss of Frame (RLOF) status bit in the Alarm 1 Status register
[ALM1; addr 047]. The RLOF criteria is set in the RLOFA, RLOFB, RLOFC,
and RLOFD bits of the Receiver Configuration register [RCR01; addr 040]. The
online framer supports the following LOF criteria for T1: 2 out of 4, 2 out of 5,
and 2 out of 6. For E1, the online framer supports 3 out of 3, with or without 915
out of 1000 CRC errors.
Once RLOF is asserted, the offline framer automatically starts searching the
receive data stream for a new frame alignment, provided that receive framing is
enabled [RABORT; addr 040]. If receive framing is disabled, the offline framer
does not automatically search for the frame alignment, but waits for a reframe
command [RFORCE; addr 040] to start a frame alignment search. If RLOF
integration is enabled [RLOF_INTEG; addr 045] the RLOF status [ALM1;
addr 047] and RLOF interrupt status [ISR7; addr 004] is integrated for 2.0 to
2.5 seconds.
N8370DSE
Conexant
2-21
CONEXANT [ CONEXANT SYSTEMS, INC ]
