BT8376EPF datasheet(79/323 Pages) CONEXANT

79 / 323 page

Bt8370/8375/8376

2.0 Circuit Description

Fully Integrated T1/E1 Framer and Line Interface

2.7 Transmit System Bus

N8370DSE

Conexant

2-51

After the offline framer recovers frame alignment, the online framer monitors

TLOF and searches for multiframe alignment; the search uses the criteria defined

by the Transmit Frame mode [TFRAME; addr 070]. The online framer conducts a

multiframe alignment search each time the offline framer recovers transmit frame

alignment, as reported by high-to-low transition of transmit loss of frame status

[TLOF; addr 048]. After TLOF recovery, the online framer searches continuously

for multiframe alignment until the correct pattern sequence is located, or until

basic frame alignment is lost (TLOF goes active-high). After multiframe

alignment recovery, the online framer checks subsequent multiframes for errored

alignment patterns, but does not use those errors as part of the criteria for loss of

basic frame alignment.

NOTE:

The online framer's multiframe search status is not directly reported to the

processor, but instead is monitored by examination of transmit error status:

TMERR, TSERR, and TCERR [addr 00B]. If the system incorporates a

certain number of multiframe pattern errors (or a certain error ratio) into

the loss of transmit frame alignment criteria, the processor must count

multiframe pattern errors to determine when to force a transmit reframe

[TFORCE; addr 071].

The frame synchronization criteria used by the offline framer is set in the

TFRAME[3:0] of the Transmit Framer Configuration register [TCR0; addr 070].

(Tables 3-15 and 3-16 illustrate supported transmit framing formats. Also, see

Tables 3-17 and 3-18, Criteria for Loss/Recovery of Transmit Frame Alignment.)

The offline framer is shared between the RCVR and XMTR and can only

search in 1 direction at a time. Consequently, the host processor can manually

arbitrate between RCVR and XMTR reframe requests by manipulating the

ABORT and FORCE controls, or by allowing the framer to automatically

arbitrate LOF requests.

The offline framer waits until the current search is complete [FSTAT;

addr 017] before checking for pending LOF reframe requests. If both online

framers have pending reframe requests, the offline framer aligns to the opposite

direction of that most recently searched. For example, if TLOF is pending at the

conclusion of a receive search which timed out without finding alignment, the

offline framer switches to search in the transmit direction. The TLOF switchover

is prevented in the preceding example if the processor asserts TABORT to mask

the transmit reframe request. TABORT does not affect TLOF status reporting. For

applications that frame in only 1 direction, framing in the opposite direction must

be masked. If, at the conclusion of a receive search timeout, TLOF status is

asserted but masked by TABORT, the offline framer continues to search in the

receive direction.

BT8376EPF Datasheet(PDF) 79 Page - Synaptics Incorporated.

BT8376EPF Datasheet(HTML) 79 Page - Synaptics Incorporated.

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