Monitoring Signal Label Byte - NEC UPD98413 User Manual

3.4.5 Monitoring Signal Label Byte

(1) Path Payload Label Unstable (Path PLU)
The µ PD98413 checks whether Signal Label, stored in the C2 byte, is received stably. Each time a frame has
been received, the value of the C2 byte is checked to see if it is the same as the value of the previous frame. If
the value of the C2 byte differs, an internal counter is incremented. When counter has been incremented up to
five, the µ PD98413 indicates this status as the Path PLU. The internal counter is reset to zero if a frame having
the same C2 byte is received three or five times (set to the MDPOHR register) continuously. Then the Path PLU
status also is terminated.
For example, if a C2 byte with one byte lost is received while C2 bytes having the expected value have been
received in succession, the counter is incremented by one when the lost byte is received and is again
incremented by one when the normal byte is next received. As a result, the counter is incremented by two.
The C2R register of the OH drop register stores the value of a C2 byte if the µ PD98413 has received the C2 byte
of the same value three or five times (set to the MDPOHR register) continuously.
(2) Signal Label Mismatch
The µ PD98413 has a function for checking the received C2 byte and detects the Path Unequipped (Path UNEQ)
and the Path Payload Label Mismatch (Path PLM).
Path UNEQ
Each time a frame has been received, a value of the C2 byte is compared with 00h. If the C2 byte is 00h, the
Path UNEQ is detected. The detection and clearing conditions are as follows.
Detection: If frames with the C2 byte being 00h are received n times continuously
Clearing: If frames with the C2 byte being the value other than 00h are received n times continuously
* n = 3 or 5. This can be selected by using the PPLMM bit of the MDPOHR register. In the default mode, n=5.
When the Path UNEQ is detected, the µ PD98413 indicates this error by the interrupt.
If the µ PD98413 is detecting LOS, LOF, LOP, L-AIS or P-AIS, the Path UNEQ is not detected.
Path PLM
Each time a frame has been received, a value of the C2 byte is compared with the expected value. If the values
do not coincide, the Path PLM is detected.
- The µ PD98413 can be set the expected value by the C2EX[7:0] bits of the MDPOHR register (Default value is
13H) , and it can be select to include in the expected value by the PPLM02 bit of the MDPOHR register.
- Note that the value of 01H is includes in the expected value, but it can be except by setting of the PPLM01 bit
of the MDPOHR register.
The detection and termination conditions are as follows.
Detection: If frames with the C2 byte Not being the expected value are received five times continuously.
Termination: If frames with the C2 byte being the expected value are received five times continuously.
* n = 3 or 5. This can be selected by using the PPLMDT bit of the MDPOHR register. In the default mode, n=5.
The default value of the C2EX field is 13H.
When the Path PLM is detected, the µ PD98413 indicates this error by the interrupt.
If the µ PD98413 is detecting LOS, LOF, LOP, L-AIS or P-AIS, the Path PLM is not detected.
CHAPTER 3 FUNCTIONAL OUTLINE
PRELIMINARY
NEC confidential and Proprietary
89