CCJ.IMUNICATIONS
SECTION 6.7
6,7,4,5
6,7,4.6
6,7.4,7
6,7,4.8
6. 7.
1
1.
9
6.7.4.10
VER.V09F
If the error check fails then a NAK is sent at the end of the
transmitted message, i.e. after the ETB or ETX. The whole of
the message is retransmitted in the event of a NAK being the
reply to a complete message block.
ETX (0311} - End of Text
ETX is transmitted after a block of characters started by an
STX. The CRC is sent immediately after an ETX, A reply is
required to indicate the receiver status,
EOT (37H) - End of Transmission
This character terminates a message transmission containing a
number of blocks, It is also used to indicate a system
malfunction,
ENQ (2DH) - Enquiry
ENQ is used as the line bid to start a transmission sequence.
EIIQ is also used to obtain a repeat transmission of
2 response,
in the case of a garbled response,
ACKO (10H,70H) - Affirmative Acknowledgement
This is one of two positive aclmowledgements to error checked
message buffers. This informs the trans,nitting station that the
message was received satisfactorily. This acknowledgement is
also used to confirm a request for the line. ACKO al tern ates
with ACK1 positive acknowledge,
Alternating Affirmative Acknowledgement
Alternating Ac:,:o and ACK1 provides sequential checking of
replies. this ensures that the bloc!,s are replied r.o c::>rrectly,
ACKO
is used as the response to a line :Jid,
It should be noted that ACKO and ACK1 consist of two 8 bit
characters.
ACK1 (10H,61H) - Positive Acknowledge
This is the alternate aclcno~led~e. It is us~d with nc:KO to
rt~sponci correctly to incomin;1, c1e33a;~es.
WACK (10H,1CH) - Wait Positive Acknowledge
A receivi~.-:; station that. ha3 corr0~~tly n~ceived
3 r:1(~ssan;.i..: but is
not yet in a con:Jition
t.) u:.;~ t.i12 d.st.::i, can scnJ n :'!t~C:\. It is
a posi ti v:2 ackn(n·Jl2d:~c. T~l~! tr~n--:s::1i t.lin~ st.Jt.i8n .::,lD'.Jld thc~n
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