2.0 Circuit Description
2.7 Transmit System Bus
Bt8370/8375/8376
Fully Integrated T1/E1 Framer and Line Interface
For applications that frame in both directions, the processor can manually
arbitrate among pending reframe requests by controlling the reframe precedence.
An example of manual control follows:
1
2
3
4
5
Initialize RABORT = 1 and TABORT = 1.
Enable RLOF and TLOF interrupts.
Read clear pending ISR interrupts.
Release RABORT = 0.
Call LOF Service Routine if either RLOF or TLOF interrupt;
{
(check current LOF status (ALMI, 2; addr 047, 048)
If RLOF recovered and TLOF lost
—Assert RABORT = 1
—Release TABORT = 0
If RLOF lost or TLOF recovered
—Assert TABORT = 1
—Release RABORT = 0
}
The status of the offline framer can be monitored using the Offline Framer
Status register [FSTAT; addr 017]. The register reports the following:
•
whether the offline framer is looking at the receive or transmit data streams
(RX/TXN)
•
•
•
•
whether the framer is actively searching for frame alignment (ACTIVE)
whether the framer found multiple framing candidates (TIMEOUT)
whether the framer found frame sync (FOUND)
whether the framer found no frame alignment candidates (INVALID)
2.7.5 Embedded Framing
Embedded framing mode [EMBED; addr 0D0] instructs the transmit framer to
search TSLIP buffer output (TNRZ) for framing bits while in T1 mode, or for
MFAS and CAS in E1 mode. Embedded framing allows the transmit timebase to
align with the transmit framer multiframe alignment of the PCM signal
transported across the system bus.
The G.802 Embedded mode supports ITU-T Recommendation G.802, which
describes how 24 T1 time slots and framing bit (193 bits) are mapped to the 32 E1
time slots (256 bits): by leaving TS0 and TS16 unassigned, by storing the 24 T1
time slots in TS1 to TS15, and in TS17 to TS25, and by storing the frame bit in
Bit 1 of TS26 (see Figure 2-20).
2-52
Conexant
N8370DSE
CONEXANT [ CONEXANT SYSTEMS, INC ]
