Computer Communication
Technical Handbook
019722-101 Rev. 05
78
SC-350/360
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The check sum for received characters in a message is derived as
follows:
The addition of every hexadecimal character value, except those for
the message start (ESC), forms the sum. The check sum is then the
sum ^255.
If any of the fault conditions listed below occurs, the computer
should wait for at least 250 ms from the time that the last character
was received before re-sending the message:
• The computer receives an incorrect check sum.
• The machine has sent NAK.
• The machine sends “invalid data”.
• The machine does not respond within 250 ms.
The machine accepts all messages when counting except the message
that sets a new batch quantity.
Note!
Messages associated with registers should be used with care during
coin counting. Under normal circumstances the counting register
should not be reset while counting is in progress.
12.3 Logging On
Note!
In the following protocols there are two operators: + and ^, where +
is arithmetic addition and ^ is logical AND.
Before any communication can occur between the computer and the
machine, the machine has to be “logged on”. This is achieved by
sending the following message:
Computer (PC)
SC-350 / SC-360
–––––––
>
ESC
–––––––
>
“Q”
–––––––
>
“F”
–––––––
>
(“Q” + “F”) ^ FF
16
<–––––––
ACK (if check sum is correct) or NAK (if check sum is
incorrect)
