DART 300 Migration Guide Difference Summary
2110291 Rev 1.0 Page 17
3.3.2.2. Packet Assembly Local Echo
Both models are capable of echoing back data as the packet assembler receivers it. This allows a
user to see what is being entered before it is sent. For most telemetry applications, this feature
should be turned off.
The DART 200 uses the
F
command: F0 to disable echo, F1 to enable it.
The DART 300 uses
+WS62
; 0 to disable echo, 1 to enable it.
3.3.2.3. Packet Forwarding
Both models will forward the packet assembly buffer based on the first of three possible events:
• Primary Forwarding Character (Manual transmission)
• Inter-character timer (Automatic transmission)
• Maximum buffer size (Maximum segment size)
The DART 300 will also forward the packet buffer if the Time Dependent Escape
Sequence (TDES) is received.
Manual Transmission
This method uses a user-defined forwarding character as a signal that the buffered packet is
complete and can be forwarded to the network.
The DART 200 supports two forwarding characters, defined in registers
S51
and
S52
. The
DART 300 supports only one character defined in register
+WS64
.
The use of this forwarding method is enabled on the DART 200 with the command
\M1
. Whether
or not to include the forwarding character in the packet is controlled with the
\F
command.
Various settings allow none, either, or both characters to be included in the packet.
The DART 300 enables the use of the forwarding character with the setting in
+WS63
; 1 enables
it and 0 disables it. The inclusion of the forwarding character in the packet is set with bit 1 of the
register:
+WS63=3
. The setting of 3 means that both bits 0 and 1 are set so the feature is enabled
and the character will be included.
The defaults are the same for both models with the feature enabled and the character included.
The default primary forwarding character is 0x0D (CR).
Automatic Transmission
This method uses a timer to measure a pause in the data stream from the local host. When the
time elapses without any data being added to the buffer, the buffer is forwarded to the network.
The DART 200 uses
S50
to set the time in tenths of second; default is 2.0 seconds. The feature is
disabled by default and enabled with the
\T1
command.
The DART 300 controls the feature with register
+WS70
. When set to zero (0), the feature is
disabled (the default), otherwise the register is the timer in tenths of a second.
Maximum Segment Size
As a safeguard in cases where both of the previous methods are disabled, both models of DART
will forward the buffer when a maximum size is reached. The DART 200 only enforces this in
TCP sessions. UDP sessions do not have the safeguard. The DART 300 enforces the maximum
on both TCP and UDP sessions.
The DART 200 does not allow user control of the maximum buffer size. The size is never greater
than 1964 bytes but will usually be less. The Maximum Segment Size reported during the TCP
session handshake determines the buffer size. This setting is part of the protocol and is not
available to the user.
The DART 300 allows the user to set the buffer size from 1 to 1000 bytes by using
+WS74
. This
size is independent of a TCP determined segment size. The TCP stack will ensure that packets
assembled from the buffer conform to network requirements.
