User's Manual

Chapter Five Specifications
Man_455U Rev 1.0 Page 33
4.4.2 Acknowledged mode
If you select any of the Acknowledged mode options, you will be asked to select a unit
address for the module. This should be a unique address for that module (0 – 127).
Auto-Connect Master
In auto-connect mode, the “master” will automatically attempt to connect to the slave address.
Once connected, the link can transfer data in either direction, with error-checking,
acknowledgement messages, and automatic re-transmissions if necessary. If the link
connection fails (indicated by the LINK led), then the master unit will automatically try to
reconnect to the slave.
At the master unit, you need to enter the address of the slave. Select the “RS232 Path”
section.. The address of the slave is entered by clicking on the “Z0” box. Up to five repeater
addresses may be entered. Repeater modules may be configured in any Acknowledged mode
option, but they must have the same system address. The repeater addresses are entered in
order from the master - that is, the leftmost address is the first repeater after the master.
You can enter address structures for four slaves - “Dest 1” to “Dest 4”. However the host
must use AT command to select which slave is required. Without the use of AT commands,
the master will only attempt to connect to the address configured in “Dest 1”.
Auto-Connect Slave
The only configuration required for a auto-connect slave module is to enter its unit address.
Single-Connect
In single-connect Acknowledged mode, the host devices use AT commands to select
destination addresses to connect to. Normally the only configuration required is a unit
address.
Acknowledged mode Options
For each Acknowledged mode, there are some options. In the “Advanced” page, there are
some timing parameters.
If you enter a “Link Check Time”, then the master unit will send a “check message” if the
check time has elapsed without any data transmissions. For example, if you enter 10 seconds,
then if there is a 10 second period without a data transmission, then the master module will
transmit a check message. If the slave does not acknowledge, then the master will transmit
the check message up to five times. If there is still no ACK, then the master will reset the
link (DCD reset).
If you enter an “Inactivity Timeout” value, then the 455U will automatically reset the link if
there has been no data transmissions within this time. If you use the link check feature, you
should enter an “Inactivity Timeout” value to reset the link at the slave unit.
It is a good idea to use these timers as it provides a higher level of security for the
Acknowledged mode system. Normally a link check time will be entered at the master unit
(for example, 10 seconds), and a inactivity timeout will be entered at the slave unit (for
example, 15 seconds). It is important that the inactivity timeout is greater than the link check
time.
A value of zero disables these parameters.