2.0 Circuit Description
CX28394/28395/28398
2.2 Receiver
Quad/x16/Octal—T1/E1/J1 Framers
2.2.10.2 RBOP Receiver
The Receive Bit-Oriented Protocol (RBOP) receiver receives BOP messages,
including the ESF Yellow Alarm, which consists of repeated 16-bit patterns with
an embedded 6-bit codeword as shown in this example:
0xxxxxx0 11111111 (received right to left)
[543210] RBOP = 6-bit codeword
The BOP message channel is configured to operate over the same channel
selected by Data Link #1 [DL1_TS; addr 0A4]. It must be configured to operate
over the FDL channel so RBOP can detect priority, command, and response
codeword messages according to ANSI T1.403, Section 9.4.1.
RBOP is enabled using the RBOP_START bit in Bit Oriented Protocol
Transceiver register [BOP; address 0A0]. BOP codewords are received in the
Receive BOP Codeword register [RBOP; addr 0A2], which contains the 6-bit
codeword, a valid flag (RBOP_VALID), and a lost flag (RBOP_LOST). The valid
flag is set each time a new codeword is put in RBOP, and is cleared on reading the
codeword. The lost flag indicates a new codeword overwrote a valid codeword
before being read by the processor.
The BOP receiver can be configured to update RBOP using a message length
filter and integration filter. The receive BOP message length filter [RBOP_LEN;
addr 0A40] sets the number of successive identical messages required before
RBOP is updated. RBOP_LEN can be set to 1, 10, or 25 messages. When
enabled, the RBOP integration filter [RBOP_INTEG; add 0A0] requires receipt
of two identical consecutive 16-bit patterns, without gaps or errors between
patterns, to validate the first codeword. RBOP integration is needed to meet the
codeword detection criteria while receiving 1/1000 bit error ratio.
The real-time status of the codeword reception can be monitored using the
RBOP_ACTIVE bit in the BOP Status register [BOP_STAT; addr 0A3]. Each
time a message is put in RBOP register, an interrupt is generated, and the RBOP
bit is set in the Data Link 2 Interrupt Status register [ISR1; addr 00A].
2-20
Conexant
100054E
CONEXANT [ CONEXANT SYSTEMS, INC ]
