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CHAPTER 6 PHY FUNCTION
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(b) Transmitting Path AIS (Path Alarm Indication Signal)
Path AIS is path remote end receive failure information that reports, to units downstream, that a failure
has been detected upstream during relay and that an alarm has been issued.
The
μ
PD98405 changes all the bits of the overhead H1, H2, and H3 bytes of the transmit frame to "1"
and, at the same time, changes all the bits in the SPE area (before scrambling) to "1" for transmission,
if the PAIS bit of the command register 1 (PCMR1) is set to 1.
Transmit overhead:
H1 through H3 bytes = all "1" & SPE bit area = all "1"
Transmission/cancellation condition:
The host controls transmission or the cancellation of
transmission by setting the PAIS bit of command register 1
(PCMR1).
(c) Transmitting Line RDI (FERF) (Line Remote Detect Indication/Far End Receive Failure)
This signal reports, to units upstream, that a line receive failure (LOS, LOF, Line AIS) has been
detected.
The
μ
PD98405 sets the sixth through eighth bits of the overhead K2 byte of the transmit frame to "110"
for transmission if the LRDI bit of the command register 1 (PCMR1) is set to 1. If an internal cause
(occurrence of LOS, LOF, Line AIS) is detected, it is transmitted automatically. This automatic
transmission upon the occurrence of an internal cause can be masked by the IACM register.
Transmit overhead:
K2 byte (6th through 8th bits) = 110
Transmission/cancellation condition:
Setting by the command register
Automatic transmission/cancellation upon occurrence of the
following internal causes (can be masked by the IACM register)
Detection/cancellation of LOF
Detection/cancellation of LOS
Detection/cancellation of Line AIS