Bt8370/8375/8376
2.0 Circuit Description
2.8 Transmitter
Fully Integrated T1/E1 Framer and Line Interface
Yellow Alarm Generation
Yellow Alarm, also referred to as RAI (Remote Alarm Indication), is a bit pattern
inserted into the transmit stream to alert far-end equipment that the local receiver
cannot recover data. Yellow Alarm/RAI is typically transmitted during Receive
Loss of Frame and is defined differently depending upon the transmit frame
format configured [TFRAME; addr 070]. Table 2-11 describes the Yellow
Alarm/RAI action taken for each frame format.
Table 2-11. Yellow Alarm Generation
Frame Format
Yellow Alarm Location
Mode
SF
Bit 2 of every time slot set to 0
Bit 2 of every time slot set to 0
YB2
YB2
(1)
ESF
SLC-96
SF/JYEL
T1DM
E1
Bit 2 of every time slot set to 0
F-bit 12 of every superframe set to 1
Y bit of the sync byte set to 0
A bit of TS0 set to 1
BY2
YJ
Y24
Y0
NOTE(S):
(1)
Yellow Alarm/RAI for T1-ESF framing is defined as a BOP priority
codeword in the FDL channel. This is called T1 Multiframe Yellow Alarm
in 8370. T1-ESF Multiframe Yellow Alarm/RAI(YF) is not transmitted
using the procedure described below. Instead, T1- ESF Multiframe Yellow
Alarm/RAI(YF) is generated by configuring DL1 to continuously transmit
an all 0s BOP priority codeword. Refer to the Transmit Data Links section
under TBOP Transmitter.
Transmission of Yellow Alarm(YB2) is controlled by the register bits listed in
Table 2-12:
Table 2-12. Yellow Alarm Register Bits
Bit Name
Register
INS_YEL
TYEL
[TFRM; addr 072]
[TALM; addr 075]
[TALM; addr 075]
[ALM1; addr 047]
[RALM; addr 045]
AUTO_YEL
RLOF
RLOF_INTEG
The insertion of Yellow Alarm(YB2) into the transmit stream is controlled by
INS_YEL. Yellow Alarm(YB2) is inserted only when INS_YEL is set.
Otherwise, these bit positions are supplied by data from TPCMI. Yellow
Alarm(YB2) generation can be done manually or automatically.
Manual generation of Yellow Alarm(YB2) is controlled by TYEL. Setting this
bit immediately and unconditionally overwrites the Yellow Alarm signal bit(s) in
the transmitted data stream with the appropriate pattern.
N8370DSE
Conexant
2-61
CONEXANT [ CONEXANT SYSTEMS, INC ]
