9XTendNEMA™
RS
‐
232/485
RF
Modem
–
Product
Manual
v2.x4x
[2007.01.04]
©
2007
MaxStream,
Inc.,
Confidential
&
Proprietary
‐
All
Rights
Reserved
59
The TT parameter (streaming limit) specifies the maximum number of bytes that the TX modem
will send in one transmission event, which may consist of many packets and retries. If the TT
parameter is reached, the TX modem will force a random delay of 1 to RN delay slots (exactly 1
delay slot if RN is zero). Each packet is counted only once toward TT, no matter how many times
the packet is retransmitted.
Subsequent packets in Acknowledged Mode are similar to those in Streaming Mode, with the addi-
tion of an ACK between each packet, and the possibility of retransmissions. Subsequent packets
are sent without an RF initializer, as the RX modems are already synchronized to the TX modem
from the preceding packet(s) and they remain synchronized for the duration of the transmission
event. Each retransmission of a packet includes an RF initializer.
Once the TX modem has sent all pending data or has reached the TT limit, the acknowledged
transmission event is completed. The TX modem will not transmit again for exactly RN delay slots,
if the local RN parameter is set to a non-zero value. The RX modem will not transmit for a random
number of delay slots between 0 and (RN-1), if the local RN parameter is set to a non-zero value.
These delays are intended to lessen congestion following long bursts of packets from a single TX
modem, during which several RX modems may have themselves become ready to transmit.
