Unitech PT600, Programming Reference Manual

Page: 67 / 77

PT600 Transmissions Packet
Transmission Format
Terminal Data STX <data> CS1 CS2 ETX
Terminal No Data EOT
Terminal response STX CMD <parameters> CS1 CS2 ETX
Acknowledgement ACK
Negative ACK NAK
Data Conversion Rules in Packet
1) One-byte data converted to two-byte data:
\ convert to \\
00 hex -- 1F hex convert to \ 80 hex -- \ 9F hex
A0 hex -- FF hex convert to \ 20 hex -- \ 7F hex
(excluding DC hex)
2) One-byte data transmitted as original data without converting:
all codes not in 1)
(including DC hex)
Data Checksum Calculation in Packet
1) CS =[sum of all characters (excluding STX and ETX) + packet
length (excluding STX and ADDR/ETX)] MOD 256
2) CS1 = high nibble of CS + 40H
3) CS2 = low nibble of CS + 40H
Example packet of command to send the file named A.EXE to PT600 with address
‘A’
Packet: STX ESC CMD <parameters> CS1 CS2 ADDR
CMD = ‘L’
<parameters> = “A . E X E “
Packet length = total characters of ESC, CMD and
<parameters> = 7
ADDR = ‘A’ + 80H = C1H
CS = [(ESC+‘L’+‘A’+’.’+’E’+’X’+’E’+ADDR)+Packet
length]
MOD 256
= [(1BH+4CH+41H+2EH+45H+58H+45H+C1H)+7] MOD 256
= 80H