Rainbow Electronics DS21458 - Manual (Page 59)

DS21455/DS21458 Quad T1/E1/J1 Transceivers
59 of 270
10.3 AIS-CI and RAI-CI Generation and Detection
The DS21455/DS21458 can transmit and detect the RAI-CI and AIS-CI codes in T1 mode. These codes
are compatible with and do not interfere with the standard RAI (Yellow) and AIS (Blue) alarms. These
codes are defined in ANSI T1.403.
The AIS-CI code (alarm indication signal-customer installation) is the same for both ESF and D4
operation. Setting the TAIS-CI bit in the T1CCR1 register and the TBL bit in the T1TCR1 register causes
the DS21455/DS21458 to transmit the AIS-CI code. The RAIS-CI status bit in the SR4 register indicates
the reception of an AIS-CI signal.
The RAI-CI (remote alarm indication-customer installation) code for T1 ESF operation is a special form
of the ESF Yellow Alarm (an unscheduled message). Setting the RAIS-CI bit in the T1CCR1 register
causes the DS21455/DS21458 to transmit the RAI-CI code. The RAI-CI code causes a standard Yellow
Alarm to be detected by the receiver. When the host processor detects a Yellow Alarm, it can then test the
alarm for the RAI-CI state by checking the BOC detector for the RAI-CI flag. That flag is a 011111 code
in the 6-bit BOC message.
The RAI-CI code for T1 D4 operation is a 10001011 flag in all 24 time slots. To transmit the RAI-CI
code the host sets all 24 channels to idle with a 10001011 idle code. Since this code meets the
requirements for a standard T1 D4 Yellow Alarm, the host can use the receive channel monitor function
to detect the 100001011 code whenever a standard Yellow Alarm is detected.