MT8930CC Просмотр технического описания (PDF) - Mitel Networks

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MT8930CC

Subscriber Network Interface Circuit

Mitel Networks 

MT8930C

Preliminary Information

Signals from NT to TE

Info0 No Signal

Info0

Info1

Info2

Info4

Valid frame structure with

all B, D, D-echo and A bits

set to ‘0’

Valid frame with data in B,

D, D-echo channels. Bit A is

set to 1.

Info3

TE State Activation Diagram

DR = 1

AR = 1

Deactivated

send Info0

DR = 1

BA = 0

Signals from TE to NT

No Signal

Continuous Signal of +‘0’, -‘0’

and six ‘1’s(1)

Valid frame with data in B & D

Bits

Where: BA(2) = Bus Activity

DR = Deactivation Request

AR = Activation Request

Sync(2) = Frame Sync Signal

A = Activation bit

Time out = 32 ms Timer Signal

Note 1: signal is not timebase locked to NT.

Note 2: Sync/BA bit of the Status Register

is configured as Sync bit when

AR = 1 and DR = 0, or as BA bit

when AR = 0 or DR = 1. A change in

the state of the AR and/or DR bits

will cause a change in the function

of the Sync/BA bit in the following

ST-BUS frame.

Activation Request

send Info1 if BA = 0

send Info0 if BA = 1

Sync = 1

BA = 0

Sync = 1

DR = 1

Activated

send Info3

Synchronized

send Info3 if Sync = 1

send Info0 if Sync = 0

A=1&

Sync = 1

Sync = 0

A=0

NT State Activation Diagram

BA = 1

AR = 1

Pending

Activation

send Info2

Deactivated

send Info0

DR = 1

AR = 1

Time out

BA =0

Pending

Deactivation

Send Info0

Sync = 1

Sync = 0

Activated

send Info4

DR = 1

Figure 7 - Link Activation Protocol, State Diagram

Line Wiring Configuration

The MT8930C can interface to any of the three

wiring configurations which are specified by CCITT

Recommendation I.430 and ANSI T1.605 (refer to

Figs. 8 to 10). These consist of a point-to-point or

one of the two point-to-multipoint configurations (i.e.,

short passive bus or the extended passive bus). The

selection of line configurations is performed using

the timing bit (B4 of NT Mode Control Register).

For an NT SNIC in fixed timing mode, the VCO and

Rx filters/peak detectors are disabled and the

threshold voltage is fixed. However, for a TE SNIC

or an NT SNIC (in adaptive timing mode), the VCO

and Rx filters/peak detectors are enabled. In this

manner, the device can compensate for variable

round trip delays and line attenuation using a

threshold voltage set to a fixed percentage of the

pulse peak amplitude.

For the short passive bus, TE devices are connected

at random points along the cable. However, for the

extended passive bus all connection points are

grouped at the far end of the cable from the NT.

Another operation can be implemented using the

SNIC in the star configuration as shown in Figure 14.

This mode allows multiple NTs, with physically

independent S-Busses, to share a common input

source and transfer information down the S-Bus to

9-44

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