X25AM Programming Manual

ITI Applications
X25AM Programming Manual—527201-001
2-15
Optimizing Output Data from 6530 Terminals
If the packet blocking mode is enabled, then data from the 6530 terminal is transmitted
in blocks of 256 bytes that contain 252 bytes of data and 4 framing characters. These
blocks are forwarded by the PAD as two 128-byte packets that are acknowledged by
the application with an ACK, which ITI puts in a packet and forwards. The ACK might
or might not be preceded by an RR packet, depending on the timing.
Figure 2-5. Data Packet Transfer with No Packet Blocking
Figure 2-6. Data Packet Transfer with Packet Blocking
VST0205.vsd
PAD
126 Bytes of Data plus
2 Framing Characters
128 Bytes of Data plus
No Framing Characters
2 Bytes of Data plus
2 Framing Characters
ITI
RR
Message
ACK inside
Data Packet
Application
ACK
(This adds a second
network round trip.)
VST0206.vsd
PAD
126 Bytes of Data plus
2 Framing Characters
126 Bytes of Data plus
2 Framing Characters
ITI
Message
ACK inside
Data Packet
Application
ACK