STP-iX455/iXL455 Series Instruction Manual
9-13
Operation
9.3.7 Error Control
• Transmit the transmission frame repeatedly from the PC when the SIM transmits "Nak"
(parity check error). When the SIM receives "Nak" from the PC, the transmission frame
is transmitted again. This operation is repeated up to 5 times.
• The SIM transmits "Ack" or "Nak" to the PC after the completion of communication
command reception. When the PC cannot receive "Ack" or "NaK" after 2 second,
retransmit the transmission frame from the PC.
When these communication statuses occur repeatedly, display to an error message or
start the error routine on the PC.
9.3.8 Transmission Frame in the RS485 Multi-point Connection
To identify a network frame and ensure the compatibility with a standard transmission
frame, add a network frame ID character " @ " and a title of 3 characters of network
frame No. to the transmission frame in the RS485 multi-point connection.
Network frame No. is specified by any 16 bits signed hexadecimal value coded ASCII
text (alphabets are in capitals) of 1 to 127 to identify the SIM.
Examples: Network frame ID character and No. in the multi-point connection
ASCII
@ 0 1
Network frame No. "1"
HEX 40
30
31
ASCII
@ 6 4
Network frame No. "100"
HEX 40
36
34
ASCII
@ 7 F
Network frame No. "127"
HEX 40
37
46
The transmission frame has a single block or multiple transmission blocks. Each
transmission block consists of a network frame ID character, a network frame No., a
start control character, data block No. (3 digits), a message (up to 255 characters), an
end control character, and a checksum (LRC). The following shows the transmission
frame when the message transmission character string is C
n
.
Transmission frame when a message is below 255 characters (n<=255):
1 2 3 4 5 6 7 8 8+n 8+n+1
8+n+2
ASCII
@ F
1
F
2
Stx
0 0 1 C
1
C
n
Etx LRC
"@" is used as a network frame ID character.
"Stx" and "Etx" are used as a start and an end character of the transmission frame
respectively.
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