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Table 10-19 lists the PAIS decodes for various payload AIS enable modes.

Table 10-19. Payload (downstream) AIS Enable Modes

PAIS[2:0]

PORT.CR1

When AIS is sent

AIS Code

000

Always

UA1

001

When LLB (no DLB) active

UA1

010

When PLB active

UA1

011

When LLB(no DLB) or PLB active

UA1

100

When LOS (no DLB) active

UA1

101

When OOF active

UA1

110

When OOF, LOS. LLB (no DLB), or

PLB active

UA1

111

Never

none

10.5.4 Loop Timing Mode

Loop timing mode is enabled by setting the PORT.CR3.LOOPT bit. This mode replaces the clock from the TCLKIn

pin with the internal receive clock from either the RLCLKn pin if the RX LIU is disabled, or the recovered clock from

the RX LIU if it is enabled. The loop-timing mode can be activated in any framing or line interface mode.

10.5.5 HDLC Overhead Controller

The data signal to the receive HDLC controller will be forced to a one while still being clocked when the framer

(DS3, E3), to which the HDLC is connected, detects LOF or AIS. Forcing the data signal to all ones will cause an

HDLC packet abort if the data started to look like a packet instead of allowing a bad, and possibly very long, HDLC

packet.

10.5.6 Trail Trace

There is a single Trail Trace controller for use in line maintenance protocols. The E3-G.832 framer has access to

the trail trace controller.

10.5.7 BERT

There is a Bit Error Rate Test (BERT) circuit for each port for use in generating and detecting test signals in the

payload bits. The BERT can generate and detect PRBS patterns up to 2^32-1 bits as well as repeating patterns up

to 32 bits long. The generated BERT signal replaces the data on the TSERn pin in SCT modes when the BERT is

enabled by setting the PORT.CR1.BENA.

When the BERT is enabled The TDENn and RDENn pins will still be active but the data on the TSERn pin will be

discarded.

10.5.8 SCT port pins

The SCT port pins have multiple functions based on the framing mode the device is in as well as other pin mode

select bits.

10.5.8.1 Transmit SCT port pins

The transmit SCT pins are TSOFIn, TSERn, TSOFOn / TDENn, and TCLKOn / TGCLKn. They have different

functions based on the framing mode and other pin mode bits. Unused input pin functions should drive a logic zero

into the device circuits expecting a signal from that pin. The control bits that configure the pins’ modes are

PORT.CR2.FM[2:0], PORT.CR3.TPFPE, PORT.CR3.TSOFOS and PORT.CR3.TCLKS.

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