User's Manual

an offline list (also known as a black list) the polling interval is not disturbed by repeated
timeouts of some slaves.
The controlling station stops polling when data is waiting to be sent to one of the slaves, or
when a slave has indicated that data is ready to send.
The controlling station stops polling when a message request is received from the eKERNEL.
The controlling station then creates a data block and sends this to the appropriate slave
address. A slave station sends data in the same fashion, but with one difference: the slave first
has to wait to be polled to tell the controlling station that data is ready to send. When a slave
is polled and has data to send, the slave tells the controlling station to stop polling. The
controlling station accepts this request by sending an ACK to the slave that wants to send data.
When it receives an ACK from the controlling station, the slave becomes temporarily master
station. Only a master station is able to send data blocks. A master station always sends data;
a slave always receives. In this scenario, the controlling station becomes (temporarily) a
slave.
Every eESPA module has a status bar with some additional information about the actual
communication situation.
• The label Receiving shows the timestamp and the latest incoming databits. Values that
can appear on this label are as follows: ACK, NAK, EOT, address + ENQ, SOH (start of
data), and data.
• The label Sent shows the timestamp and the databit that was last sent. Values that can
appear on this label are as follows: ACK, NAK, EOT, address + ENQ, SOH (start of data),
and data.
• The Local address field shows the defined value of eESPA_LocalAddress_n in the eESPA
table. Avaya recommends that you set the controlling station local address to 1. The field
eESPA_ControlStation_b in the eESPA table defines whether this module is a controlling
station or not.
In the DECT Messenger model, a module always communicates with one other module
(master to slave or point to point). The address of the other station is defined in the
eESPA_ExternalAddress_n field in the eESPA table. In the case of a non-controlling
module (defined by setting eESPA_ControlStation_b on No in the database), for example,
you can use a local address of 2 and an external address of 1. In this case, the module
communicates directly with the controlling station.
• The label Status shows log information to allow users to see special actions.
Figure 75: Status of master/slave on page 125 shows an example of the eESPA status bar.
Figure 75: Status of master/slave
Data flow
DECT Messenger Installation and Commissioning — Book 1 March 2012 125