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									Team Conferencing Systems

RS366 Interface Description




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Contents

............................................................................................................................................ Page

About this document                                                                                                                        2
Overview                                                                                                                                   3
IDLE                                                                                                                                       6
DIALING ONE                                                                                                                                6
DIALING TWO                                                                                                                                7
CONNECTING                                                                                                                                 7
CONNECTED                                                                                                                                  8
ANSWERING                                                                                                                                  8
INCOMING ONE                                                                                                                               9
INCOMING TWO                                                                                                                               9
ABORTING                                                                                                                                  10
DISCONNECTING                                                                                                                             10
Ladder diagrams                                                                                                                           12
Timer Values                                                                                                                              14
Differences between the TC and the Leadership Conferencing (LC) system                                                                    15




About this document
The following conventions are used throughout this document
Interface calls to/from other program modules are in mixed case Courier font: oa_mkcall
States are in Italic: Dialing One
Messages to other program modules are in upper case Courier font: WAITCALL




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Overview
The RS366 interface in conjunction with the V.35/RS449 interface is used by the Enterprise TC system to
control external Network interface equipment. The RS366 interface controls call set up and dialing through
the DDM card in the Enterprise TC.

The software that resides in the Enterprise TC realizes a state machine that handles the interaction between
the TC and other Network equipment. This document outlines the operation of that state machine. The term
Modem Control Lines refers to the follow:-

RS366

PND - Present Next Digit
ACR - Abandon Call and Retry
DLO - Data Line Occupied
DSC - Distant Station Connected

(PWI- Power Indication)is not monitored)

V.35/RS449

RI - Ring Indicate
CTS - Clear To Send
DCD - Data Carrier Detect

(DSR - Data Set Ready is not Monitored)
Included at the end of this document are three ladder diagrams outlining the typical operation of the
interface.




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   State Transition Table

                                                                                  Next State
                   Idle           Dial 1          Dial 2          Connecting      Connected      Answering       Incoming 1      Incoming 2      Abort          Disconnect
  Idle             No Modem       Make Call                                                      DCD Active      RI Active
                   Activity
  Dialing 1        ACR Active                     PND Active                                                                                     ACR Active
S                  or TimeOut1                                                                                                                   or TimeOut1
t Dialing 2        ACR Active     PND                             PND released PND                                                               ACR Active
a                  or TimeOut1    released and                    and no more  released and                                                      or TimeOut1
                                  more digits                     digits       no more
r
                                                                               digits and
t                                                                              DCD Active
  Connecting       ACR Active                                     DSC Active   DCD is
S                  or TimeOut1                                                 active
t Connected        No Modem                                                                                                                                     DCD
a                  Activity                                                                                                                                     released and
t                                                                                                                                                               other modem
e                                                                                                                                                               activity or
                                                                                                                                                                oa_relcall is
                                                                                                                                                                issued
  Answering        ACR Active                                                     oa_ackcall                                                     ACR Active     os_ackcall
                   or TimeOut1                                                    accepts the                                                    or TimeOut1    rejects the
                                                                                  call                                                                          call
  Incoming 1                                                                      oa_ackcall                                     oa_ackcall
                                                                                  accepts the                                    accepts the
                                                                                  call and                                       call
                                                                                  DCD is
                                                                                  Active
  Incoming 2       TimeOut1 or                                                    DCD is                                                                TimeOut1 or
                   No Modem                                                       Active                                                                No Modem
                   Activity                                                                                                                             Activity
  Abort            No Modem                                                                                                                             No Modem
                   Activity                                                                                                                             activity
  Disconnected     No Modem
                   Activity
   Notes 1: There is an intermediary state, AbortorIdle. The software checks the modem control lines before a transition to the next state. If there is any activity on the RS366
              interface then Abort is entered otherwise it is Idle.
          2: The modem control lines are RS366:               PND - Present Next Digit, ACR - Abandon Call and Retry, DLO - Data Line Occupied, DSC - Distant Station Connected
                                             V.35/RS449: RI - Ring Indicate, CTS - Clear To Send, DCD - Data Carrier Detect


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IDLE

Description
Idle is the state during which no call is active; code is waiting for a dial command for an outgoing call
(oa_mkcall) or for an incoming call (WAITCALL).

Modem Control Lines
In this state all modem controls are held inactive.

Normal Transitions
Dialing One is entered in response to a dialing command through oa_mkcall. The transition is
        accomplished by calls to ControlSigWrite (to assert DTR) and to SetCRQ (to assert CRQ
        and start the RS-366 dialing process) from oa_mkcall.).
Connected is entered in response to a VTEL Immediate connection command through oa_mkcall. The
        transition is accomplished by calls to ControlSigWrite (to assert DTR and RTS) and to
        DetectDDM_Freq (to detect the clock rate and set the clock reference for the port) from
        oa_mkcall. Sends MAKECALLACK.
Incoming One is entered for an incoming manual call when RI goes active. This transition is accomplished
        by interrupt code handling the control line change. Sends WAITCALL.
Answering is entered for an incoming automatic call when DCD goes active. This transition is
        accomplished by interrupt code handling the control line change. Sends WAITCALL.

Error Conditions/Transitions
SetCRQ could return a dialing error which should be returned to the caller of oa_mkcall.

Don’t Cares
For VTEL Immediate mode, the RI, DSC, and DCD lines are ignored completely; no incoming calls are
recognized in VTEL Immediate mode.
We always ignore DSR and CTS from the V.35/RS-449 interface and PWI from the RS-366 interface.




DIALING ONE

Description
Dialing One is the state during which the code waits to send the next dialing character in response to PND
from the RS-366 dialer interface.

Modem Control Lines
In this state DTR and CRQ have already been set active. RTS is held inactive.

Normal Transitions
Dialing Two is entered upon assertion of PND. This transition is accomplished by interrupt level code
        upon assertion of PND. The interrupt handler code places the next dialing character on the NBn
        lines and asserts DPR.




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Error Conditions/Transitions

If ACR is asserted while awaiting assertion of PND, the call is aborted through Aborting. If the timer times
out then an intermediary state results that resolves whether an Abort or Idle state follows. The values for the
timer can be found at the end of this document.

Don’t Cares
RI is ignored until we understand how to treat it as an error.
DSC and DCD are ignored; they will be noticed later (from Connecting).
We always ignore DSR and CTS from the V.35/RS-449 interface and PWI from the RS-366 interface.




DIALING TWO

Description
Dialing Two is the state during which the code waits for release of PND from the RS-366 dialer interface
signaling the dialer’s acceptance of the current dialing character.

Modem Control Lines
In this state DTR, CRQ and DPR have already been set active. RTS is held inactive.

Normal Transitions
Dialing One is entered upon release of PND if there are more characters in the dialing string. This
        transition is accomplished by interrupt level code upon release of PND. The interrupt handler code
        releases DPR.
Connecting is entered upon release of PND if there are no more characters in the dialing string and DCD is
        not yet asserted. This transition is accomplished by interrupt level code upon release of PND. The
        interrupt handler code releases DPR and asserts RTS. If DSC is already asserted, CALLSTATUS
        is sent.
Connected is entered upon release of PND if there are no more characters in the dialing string and DCD is
        already asserted. This transition is accomplished by interrupt level code upon release of PND. The
        interrupt handler code releases DPR and asserts RTS. MAKECALLACK is sent.

Error Conditions/Transitions
If ACR is asserted while awaiting release of PND, the call is aborted through Aborting.
If the timer times out then an intermediary state results that resolves whether an Abort or Idle state follows.
The values for the timer can be found at the end of this document.

Don’t Cares
We always ignore DSR and CTS from the V.35/RS-449 interface and PWI from the RS-366 interface.




CONNECTING

Description
Connecting is the state during which the code waits for the assertion of DCD to indicate an outbound call
has completed.




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Modem Control Lines
In this state DTR, RTS and CRQ have already been set active.



Normal Transitions
Connected is entered upon assertion of DCD. MAKECALLACK is sent.
Should DSC be asserted before DCD, CALLSTATUS is sent and code remains in Connecting.

Error Conditions/Transitions
If the timer times out then an intermediary state results that resolves whether an Abort or Idle state follows.
The values for the timer can be found at the end of this document.

Don’t Cares
We always ignore DSR and CTS from the V.35/RS-449 interface and PWI from the RS-366 interface.




CONNECTED

Description
Connected is the state during which a call is active.

Modem Control Lines
In this state DTR and RTS have already been set active. All other lines are inactive.

Normal Transitions
Disconnecting is entered upon either of the following conditions: a call is made to oa_relcall (we hang
          up); or DCD is released (they hang up). In either case, DTR and RTS are immediately released and
          Disconnecting is entered to wait for appropriate conditions for a return to Idle.
Idle is entered upon the release of DCD and the detection of no other modem control line activity.

Error Conditions/Transitions
None.

Don’t Cares
We always ignore DSR and CTS from the V.35/RS-449 interface and PWI from the RS-366 interface.




ANSWERING

Description
Answering is the state during which the code waits for oa_ackcall in response to the WAITCALL sent
for an automatic incoming call.

Modem Control Lines
In this state control lines are held inactive awaiting response to the WAITCALL.

Normal Transitions


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Connected is entered upon receipt of oa_ackcall accepting the call. Code in oa_ackcall
        accomplishes the transition and asserts DTR and RTS via a call to ControlSigWrite.
        WAITCALLACK is sent.
Disconnecting is entered upon receipt of oa_ackcall rejecting the call. Code in oa_ackcall
        accomplishes the transition.

Error Conditions/Transitions
If DCD is released prior to receipt of oa_ackcall, then oa_ackcall will result in an error indicating
no call is active and a transition to Idle (if RI is also inactive) or Disconnecting (if RI is asserted).
 If the timer times out then an intermediary state results that resolves whether an Abort or Idle state follows.
The values for the timer can be found at the end of this document.



Don’t Cares
We always ignore DSR and CTS from the V.35/RS-449 interface and PWI from the RS-366 interface.




INCOMING ONE

Description
Incoming One is the state during which the code waits for oa_ackcall in response to the WAITCALL
sent for a manual incoming call.

Modem Control Lines
In this state all modem controls are held inactive.

Normal Transitions
Incoming Two is entered upon receipt of oa_ackcall accepting the call. Code in oa_ackcall
        accomplishes the transition and asserts DTR and RTS via a call to ControlSigWrite.
        WAITCALLACK is sent.
Disconnecting is entered upon receipt of oa_ackcall rejecting the call. Code in oa_ackcall
        accomplishes the transition.
Connected is entered if DCD is asserted directly after the accepting the call

Error Conditions/Transitions
If RI is released prior to receipt of oa_ackcall, then oa_ackcall will result in an error indicating no
           call is active and a transition to Idle (if DCD is also inactive) or Disconnecting (if DCD is
           asserted).

Don’t Cares
We always ignore DSR and CTS from the V.35/RS-449 interface and PWI from the RS-366 interface.




INCOMING TWO

Description



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Incoming Two is the state during which the code waits for assertion of DCD to indicate the incoming
manual call is completely connected.

Modem Control Lines
In this state DTR and RTS have already been set active.

Normal Transitions
Connected is entered upon assertion of DCD. This transition is accomplished by interrupt level code upon
        assertion of DCD. WAITCALLACK is sent.

Error Conditions/Transitions
If the timer times out then an intermediary state results that resolves whether an Abort or Idle state follows.
The values for the timer can be found at the end of this document.

Don’t Cares
We always ignore DSR and CTS from the V.35/RS-449 interface and PWI from the RS-366 interface.




ABORTING

Description
Aborting is the state during which the code waits for an idle line condition after aborting a call.

Modem Control Lines
In this state all modem controls are held inactive.

Normal Transitions
Idle is entered upon release of both RI and DCD. This transition is accomplished by interrupt code
          monitoring the lines.

Error Conditions/Transitions
None.

Don’t Cares
We always ignore DSR and CTS from the V.35/RS-449 interface and PWI from the RS-366 interface.




DISCONNECTING

Description
Disconnecting is the state during which the code waits for an idle line condition after a normal call
termination (local or remote hang up).

Modem Control Lines
In this state all modem controls are held inactive.

Normal Transitions




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Idle is entered upon release of both RI (if not in VTEL Immediate mode) and DCD. This transition is
          accomplished by interrupt code monitoring the lines. RELCALL is sent indicating the end of the
          call.

Error Conditions/Transitions
There could be a time-out here, but what could we do? We already dropped all of our lines.

Don’t Cares
We always ignore DSR and CTS from the V.35/RS-449 interface and PWI from the RS-366 interface.




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 Ladder diagrams
 Outgoing dialed call


 DTE                                Signal change                   ACE

 Idle
 oa_mkcall
 Dialing 1 - Wait for PND          PND asserted
 Dialing 2
                                    Set DPR and CRQ
 Present first digit
                                    Set NB1,2,4,8

                                    PND Cleared

 Dialing 1                          Clear CRQ

 - repeat from  until last digit
 sent
 Connecting                         DSC set

Bring up 449 interface wait for DCD Set DTR +RTS

                 OR
                                    DCD (V.35) set

                                    Clear all Modem control lines


 Connected




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Incoming call


DTE                        Signal change             ACE

Idle                       RI active

Incoming 1
oa_ackcall accepts call
Incoming 2                 DCD Active

Connected




Disconnecting a call


DTE                        Signal change             ACE

Connected                  DCD inactive

Disconnecting
                           All Modem line inactive

Idle




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Timer Values

There is a 3 minute timer for the incoming call to be accepted and transition from Incoming 1 to Connected.

Dialing must be completed within 3 minutes. A timer is started when Dialing One is entered and stopped
when Connecting is entered.

If RI is dropped during Incoming 1 state then there is 10 seconds to re-establish the signal before the timer
times out.




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Differences between the TC and the Leadership Conferencing
(LC) system

Clock Source

The clock source that is provided to the TC must be within 200Hz of the target frequency. For example
when running at 384 kbs it must be between 283.8 and 384.2.

RS449 control lines

The TC monitors DCD- Data Carrier Detect line to establish a connection an ignores CTS- Clear To Send
and DSR - Data Set Ready
The LC monitors CTS and DSR to establish a connection and ignores DCD

RS366

The TC monitors DLO - Data Line Occupied wheras it ignored by the LC.




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