Free Buffer Enquiries
•
•
•
•
An ALERT BURST
An SOH (Start Of Header--ASCII code 01H)
An SID (Source ID) character
Two (repeated) DID (Destination ID)
characters
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.
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.
A Free Buffer Enquiry is used to ask another node
if it is able to accept a packet of data. It is sent by
the following sequence:
• An ALERT BURST
• An ENQ (ENQuiry: ASCII code 85H)
•
•
Two (repeated) DID (Destination ID)
characters
ALERT
BURST
ENQ
DID
DID
•
•
Data Packets
A Data Packet consists of the actual data being
sent to another node. It is sent by the following
sequence:
ALERT
SOH
SID
DID
DID
COUNT
data
data
CRC
CRC
BURST
12
DISCONTINUED DATASHEET
SMSC [ SMSC CORPORATION ]
