Nortel DMS-10 Series Installation, Operation And Maintenance Manual page 437

schedules are a function of the expected traffic at the various CO sites. The
HOC can request status, a file transfer, or abort the session. All of these
activities must be initiated by the HOC.
BMC Communication
The HOC initiates remote operation through a modem over either dial-up or
dedicated lines. The modem links are capable of transmitting data at speeds
of 1200, 2400, 4800, and 9600. The communications protocol used is
BISYNC for 1200, 2400, 4800, and 9600 baud.
Note: The BMC BISYNC System with the common hardware platform
can communicate data using the RS-232 or V.35 interface. The software
limits the maximum baud rate to 9600 baud.
When the HOC requests a session connect, the incoming modem receives the
HOC modem's carrier signal and automatically responds with carrier detect.
The incoming modem is connected through the Power and Alarm
Communication PCA, which communicates with the active processor. The
modem attached to the BMC transmits a carrier that is recognized by the
HOC modem and the physical link is established, and the HOC and BMC are
in Contention mode. HOC bids for the line by transmitting an ENQ message
to the BMC. The BMC acknowledges the HOC bid for control of the line
with an ACK0 message. The HOC goes into Talker mode, and transmits a
Text message containing the HOC password and the poll request. This HOC
password must match the polling password of the BMC. If this message is
not in the proper form or the password is incorrect, the BMC (in Listener
mode) transmits an EOT message and then an DLE EOT message to the HOC
to abort the session. If the Text message is valid, the BMC transmits an
Acknowledgment (ACK1) message. After the acknowledgment, the HOC
sends the session back into Contention mode with an EOT message. The
BMC then bids for the line with transmission of an ENQ message. HOC
responds with an ACK0 message. After receipt of the acknowledgment, the
BMC goes into Talker mode and begins transmission of the polling data as
Text messages. The HOC, in Listener mode, acknowledges the receipt of the
Text messages with ACK0/ACK1 message (alternating). After all of the data
has been transmitted, the BMC sends an Disconnect (DISC) message. The
HOC responds with an ACK0/ACK1 message. The BMC then transmits an
EOT message and an DLE EOT message to end the session.
BMC Status Request
The BMC CPU monitors and reports BMC activity and the status of the files
on the system through activity reports. Upon request, the BMC transmits any
available report to the HOC. These reports inform the HOC of BMC activity,
indicating whether files are open for read, open for write, closed, transmitted,
or unequipped. This informs the HOC what the BMC is doing and which
files are primary (unpolled) or secondary (polled).
BMC II BISYNC Operation, Administration, and Maintenance Guide BMCB001 and up
Section 060-INDP-510 System Operation Guide 5-7