XRT7250 Datasheet, PDF (259/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

XRT7250
DS3/E3 FRAMER IC
REV. 1.1.1
áç
TXASOURCESEL[1:0]
SOURCE OF A BIT
01
Transmit Overhead Data Input Interface
10
Transmit Payload Data Input Interface
11
Functions as a FEBE (Far-End-Block Error) bit-field.
This bit-field is set to "0", if the Near-End Receive Section (within this chip) detects no BIP-4
Errors within the incoming E3 frames.
This bit-field is set to "1", if the Near-End Receive Section (within this chip) detects a BIP-4
Error within the incoming E3 frame.
Configuring the Transmit Payload Data Input Interface
block to accept the “N” Bits from the Terminal Equip-
ment, then the user must write the value “11” into the
TxNSourceSel[1:0] bit-fields. Once the user does
this, then any value, which resides on the TxSer input
pin, when the “N” bit is being processed by the Trans-
mit Section will be inserted into the “N” bit-field within
the very next outbound E3 frame.
For completeness, the relationship between the con-
tents of the TxNSourceSel[1:0] bits and the resulting
source of the “N” bit is listed below.
Bits 4, 3, TxNSourceSel[1:0]
These two Read/Write bit-fields combine to specify
the source of the N-bit, within each outbound E3
frame. The relationship between these two bit-fields
and the resulting source of the N Bit is tabulated be-
low.
TXNSOURCESEL[1:0]
00
01
10
11
SOURCE OF N BIT
TxE3 Service Bits Register (Address = 0x35)
Transmit Overhead Data Input Interface
Transmit LAPD Controller
Transmit Payload Data Input Interface.
240