PM8313 datasheet(53/192 Pages) PMC

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PM8313 D3MX

DATA SHEET

PMC-920702

ISSUE 5

M13 MULTIPLEXER

DS1 payload loopback can be activated or deactivated under software control.

During payload loopback the DS1 stream being looped back still continues

unaffected in the demultiplex direction. The second and fourth demultiplexed

DS1 streams are logically inverted, and all four demultiplexed DS1 streams can

be replaced with AIS on an individual basis.

Similar functionality supports CCITT Recommendation G.747. The FIFO is still

required for rate adaptation. The frame alignment signal and parity bit are

generated and inserted by the timing circuitry. Software control is provided to

transmit Remote Alarm Indication (RAI), high speed signal AIS, and the reserved

bit. A diagnostic option is provided to invert the transmitted frame alignment

signal and parity bit.

When demultiplexing three 2048 kbit/s streams from a G.747 formatted 6312

kbit/s stream, the MX12 performs bit destuffing via interpretation of the C-bits.

Tributary payload loopback can be activated or deactivated under software

control. Although no remote loopback request has been defined for G.747,

inversion of the third C-bit triggers a loopback request detection indication in

anticipation of Recommendation G.747 refinement. All three demultiplexed 2048

kbit/s streams can be replaced with AIS on an individual basis.

8.11

Loopback Modes

DS3 Diagnostic Loopback allows the transmitted DS3 stream to be looped back

into the receive DS3 path, overriding the DS3 stream received on the

RDAT/RPOS and RNEG/RLCV inputs. The RCLK signal is also substituted with

the transmit DS3 clock, TCLK. While this mode is active, AIS may be substituted

for the DS3 payload being transmitted on the TPOS/TDAT and TNEG/TMFP

outputs. The configuration of the receive interface determines how the

TNEG/TMFP signal is handled during loopback: if the UNI bit in the DS-3 FRMR

is set, then the receive interface is configured for RDAT and RLCV, therefore the

TNEG/TMFP signal is suppressed during loopback so that transmit MFP

indications will not be seen nor accumulated as input LCVs; if the UNI bit is clear,

then the interface is configured for bipolar signals RPOS and RNEG, therefore

the TNEG is fed directly to the RNEG input. This loopback mode is shown

diagrammatically, below:

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