Data Packets
A single COUNT character which is the 2's
complement of the number of data bytes to
follow if a short packet is sent, or 00H
followed by a COUNT character if a long
packet is sent
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A Data Packet consists of the actual data being
sent to another node. It is sent by the following
sequence:
N data bytes where COUNT = 256-N (or 512-
N for a long packet)
Two CRC (Cyclic Redundancy Check)
characters. The CRC polynomial used is:
X16 + X15 + X2 + 1.
·
·
An ALERT BURST
An SOH (Start Of Header--ASCII code 01H)
An SID (Source ID) character
Two (repeated) DID (Destination ID)
characters
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·
·
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(ACK)
(NAK)
Acknowledgements
Negative Acknowledgements
An Acknowledgement is used to acknowledge
reception of a packet or as an affirmative
response to FREE BUFFER ENQUIRIES and is
sent by the following sequence:
A Negative Acknowledgement is used as a
negative response to FREE BUFFER
ENQUIRIES and is sent by the following
sequence:
An ALERT BURST
An ACK (ACKnowledgement--ASCII code
86H) character
An ALERT BURST
A NAK (Negative Acknowledgement--ASCII
code 15H) character
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ALERT
BURST
ACK
ALERT
BURST
NAK
11
SMSC [ SMSC CORPORATION ]
