MK50H27(1997) 데이터 시트보기 (PDF) - STMicroelectronics

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MK50H27
(Rev.:1997)

Signalling System 7 Link Controller

STMicroelectronics 

MK50H27

T / TTC D

M

D / TTC T

Tin

Tie

m

SUERM THRESHOLD. Number of consecutive signal units received

in error that will cause an error rate high indication. When operating

in TTC compliant mode (CSR2 JSS7E=1), this field should contain the

D value (typically 16) used for TTC JT-Q703 SUERM operation.

PROVING ABORT LIMIT. Number of consecutive aborted proving

periods that cause the MK50H27 to return to the OUT-OF-SERVICE

state.

SUERM ERROR RATE. The lowest acceptable number of signal

units per signal unit error. When operating in TTC compliant mode

(CSR2 JSS7E=1), this field should contain the T SUERM Threshold

value (typically 285) used for TTC JT-Q703 SUERM operation. This

field should be expressed as a two’s complement value.

NORMAL AERM THRESHOLD. Number of signal unit errors that

cause the abortion of a normal proving period.

EMERGENCY AERM THRESHOLD. Number of signal unit errors

that cause the abortion of an emergency proving period.

Maximum frame length. Number of bytes allowed in the information

portion of received MSUs before octect counting begins.

NOTE:

The operation of the SUERM (Signal Unit Error Rate Monitor) is different between CCITT / ITU compliant

systems and TTC JT-Q703 compliant systems. Although both SUERM schemes operate based upon a

leaky bucket principle, there are some major differences in their implementation.

For CCITT/ITU Q.703 the SUERM count is incremented by 1 for each errored SU received until a thresh-

old T (typically 64) is reached, at which time a link failure is declared.. For every D (typically 256) good

SUs received the SUERM Count, Cs, is decremented by 1 (not to go less than 0).

For TTC JT-Q703 the SUERM count is updated once every monitor time Te (typically 24 ms) regardless

of the number of SUs received during the time Te. If the last SU received was errored, then the SUERM

count is incremented by D (typically 16) when Te expires. If the last SU received was good, then the

SUERM count is decremented by 1 (not to go less than 0) when Te expires. If the SUERM count should

ever reach the threshold T (typically 285), then a link failure is declared. For the MK50H27 the value

used for time Te is the same value as programmed for time Tf (typically 24 ms for both).

Due to this difference in SUERM operation, the fields in the MK50H27 Initialization Block that are used

for D and T are exchanged if JSS7E=1 selecting Japanese SS7 (TTC JT-Q703 compliance).

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