User`s manual

EM1500 User’s Manual www.rabbit.com 99
B.2.1.5 Other Packetization Controls
The “Max buffer” field in the Protocol dialog allows some control over the maximum amount of packet
data to accumulate. In the above description of the idle timing mode, it was mentioned that a maximum of
1020 characters can be buffered. If desired, this limit can be reduced by setting this field to a value less
than 1020. If it is set to, say, “10” then as soon as ten characters have been received from the network, the
data will start being transmitted to the serial port. This may be useful if the network latency is low, and it is
desired to start transmitting the packet even before the EOP indicator has been received. This is usually
only needed for idle packetizing mode, and is done in the hope that the rest of the packet will arrive before
the serial port transmitter becomes “starved.”
The “Trailing chars” field in the Protocol dialog is only useful with the string packetization modes. It spec-
ifies an additional number of characters which follow the terminating string that are to be considered part
of the packet. For example, some protocols may require a 2-byte checksum to be appended after the final
CRLF that terminates the packet data. In this case, the “Trailing chars” field should be set to “2” to ensure
that the checksum gets transmitted along with the packet.