DS2155 datasheet(57/262 Pages) DALLAS

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DS2156

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8.2

T1 Transmit Transparency

The software signaling insertion-enable registers, SSIE1–SSIE4, can be used to select signaling insertion

from the transmit signaling registers, TS1–TS12, on a per-channel basis. Setting a bit in the SSIEx

In transparent mode, bit 7 stuffing and/or robbed-bit signaling is prevented from overwriting the data in

the channels. If a DS0 is programmed to be clear, no robbed-bit signaling is inserted nor does the channel

have bit 7 stuffing performed. However, in the D4 framing mode, bit 2 is overwritten by a 0 when a

Yellow Alarm is transmitted. Also, the user has the option to globally override the SSIEx registers from

determining which channels are to have bit 7 stuffing performed. If the T1TCR1.3 and T1TCR2.0 bits are

set to 1, then all 24 T1 channels have bit 7 stuffing performed on them, regardless of how the SSIEx

registers are programmed. In this manner, the SSIEx registers are only affecting the channels that are to

have robbed-bit signaling inserted into them.

8.3

AIS-CI and RAI-CI Generation and Detection

The DS2156 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 DS2156 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 DS2156 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.

DS2155 Datasheet(PDF) 57 Page - Dallas Semiconductor