H - keep message i - wait for host connection – Verilink 9000 Series (34-00271) Product Manual User Manual
Page 195
Legacy Terminal Options
173
H - Keep Message
Even though one of the principles of the MultiPro platform is that it should never
lose a message, there are times when the MultiPro unit may determine that a
message should be discarded. One of those times is if the MultiPro unit is trying to
deliver a message to a device and the device NAKs the message. The MultiPro unit
tries to deliver the message once and then retries four times. If the device still
refuses to accept the message, the MultiPro unit discards the message. When this
option is set, the MultiPro platform does not discard the message but continually
tries to deliver it.
A very specific sequence of events need to occur for a message to be discarded.
Simply NAKing the message is not enough. As shown in Figure 10-14, the device
must first ACK the select the MultiPro platform sends to determine if the device is
ready to receive a message. If the device acknowledges that it is ready to receive a
message, but NAKs the actual message the MultiPro unit sends, is considered one
sequence. If this occurs a total of five times, the message is discarded. This is
because the MultiPro platform needs to determine if a message has been corrupted
and therefore needs to be discarded.
I - Wait
For Host
Connection
There may be times when it is desirable to poll a device only when the host is
on-line. One such application is when automated teller machines (ATMs) are
connected to the MultiPro platform. Most ATMs rely on polling frequency to
determine if the host is on-line. If they are being polled, they consider the host to
be on-line, likewise, if there is no polling, they consider the host off-line. They can
then initiate pre-programmed sequences to notify potential customers that they are
disabled for lack of host access.
DOWNLOAD CONFIG
MODE BACKUP
NET
ALARM POWER
PRISM 9111
T
R
A
N
S
P
O
R
T
®
Terminal
Select
ACK
NAK
Message
Sequence sent once; then
four retries; then the
message is discarded.
Figure 10-14 Message Discarded