BT8376EPF datasheet(214/323 Pages) CONEXANT

214 / 323 page

Bt8370/8375/8376

3.16 Data Link Registers

Fully Integrated T1/E1 Framer and Line Interface

3-96

Conexant

N8370DSE

FFC[5:0]

Near Full FIFO Threshold—Selects FIFO depth of near full interrupt [RNEAR; addr 009] and

near full level status [RNEAR1; addr 0A9]. The RNEAR interrupt and RNEAR1 indicator are

both activated when the number of empty FIFO locations equals the selected threshold. The

threshold controls how many data and/or status bytes (64 minus threshold value) that the

processor must read from RDL1 after the RNEAR interrupt so it can clear the RNEAR1

indicator. The threshold also determines how much time remains (in bytes) for the processor to

read RDL1 before the receive FIFO is full. If a receive message is in progress when the near

full threshold is reached, the receiver issues a message interrupt [RMSG; addr 009] and places

a Partial message in the receive FIFO.

0A8—Receive Data Link FIFO #1 (RDL1)

Two different read byte values are supplied: WORD0 equals message status, and WORD1 equals message data.

The processor determines which byte value is located in the FIFO by reading the receiver data link status

[RDL1_STAT; addr 0A9]. In some cases, multiple consecutive status bytes can be placed in the FIFO, so the

processor must always read RDL1_STAT before reading RDL1. This allows it to distinguish between WORD0

and WORD1 byte values. However, each time a non-0 byte count [RDL1_CNT] status is read, the processor is

guaranteed that the next byte read from RDL1 will be message data [WORD1], not message status. Status byte

and a message data byte each occupy 1 byte of FIFO space.

WORD0: Message Status

EOM[1, 0]

End of Message—Receive data link reports an End of Message status for each occurrence of a

complete (Good), a continued (Partial), an errored (FCS/Non-integer), or an aborted (Abort)

message.

Properly received unformatted messages are reported with a Partial end of message status.

The processor responds to Good or Partial status by reading the indicated number of data bytes

[RDL1_CNT] from RDL1. For abort or error cases, RDL1_CNT equals 0 to indicate all that

received data from that message was discarded.

A Good status with RDL1_CNT=0 is reported if the processor reads RDL1 while the

receiver is in progress of filling the FIFO (in which case RDL1_STAT contains RSTAT1=1 and

RMSG1=1). If an abort or error status with zero byte count is reported after the processor has

already buffered a prior HDLC partial message, that partial buffered processor data should be

discarded.

FFC[5:0]

Empty @ RNEAR

Filled @ RNEAR

00 0000

none

64 = RFULL

00 0001

1 empty FIFO location

63 filled

00 0010

2 empty FIFO locations

62 filled

11 1110

64 empty FIFO locations

1 filled

11 1111

63 empty FIFO locations

0 filled = empty

EOM[1]

EOM[0]

RDL1_CNT[5]

RDL1_CNT[4]

RDL1_CNT[3]

RDL1_CNT[2]

RDL1_CNT[1]

RDL1_CNT[0]

BT8376EPF Datasheet(PDF) 214 Page - Synaptics Incorporated.

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