Universal Menu Book/Interface/RS232 options/Handshaking

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Data flow control is available using either hardware (Modem, Busy/Ready) or software (XON/XOFF). In addition, an optional acknowledgement control is available (ACK/NAK with or without error response). Flow control may be combined with acknowledgement control. The RS232 voltage levels employed by most readers for transmission are either -10V (OFF) or +10V (ON).

1. No handshake:
Does not employ any handshaking: data is transmitted regardless of the control signals. This option will undo any handshake and flow control options selected.

2. Busy/ready:
The reader s RTS is ON as soon as the power is supplied to the reader and will stay ON while the reader can receive data from the host. The host will keep the reader s CTS ON while it is ready to receive data from the reader. While CTS is ON the reader is able to transmit data. The reader will abort transmission with an error indication of the buzzer when the CTS is not ON within a certain configurable period. The reader may drop RTS to OFF during transmission if it can not receive data simultaneously. See figure 2.04.

File:HandshakingBusyReady.svg

3. Modem mode:
The reader s RTS is OFF as soon as power is supplied to the reader. The reader will turn RTS ON when it wants to transmit data to the host. The host should respond by putting CTS ON when it is ready to receive data. While CTS is ON the reader is allowed to transmit data. When all data has been transmitted, the reader will turn RTS OFF. In response, the host should turn OFF the reader s CTS. If, while RTS is ON, the CTS line is not ON for a certain configurable period, the reader will terminate the transmission with an error indication of the buzzer. See figure 2.05.

File:HandshakingModem.svg

4. XON/XOFF:
The reader sends data until an XOFF (ASCII DC3, Hex 13) character is received from the host. Only when the reader receives an XON (ASCII DC1, Hex 11) character, the reader continues to send its data.

5. ACK/NAK:
After data has been transmitted, the reader expects to receive one of the following responses from the host:

Response: "ACK" (ASCII: Hex 06)
Action: The reader completes transmission with the good-read buzzer.

Response: "NAK" (ASCII: Hex 15)
Action: The reader sends the data again.

Response: "DC1" (ASCII: Hex 11)
Action: The reader completes transmission without a good-read or error buzzer.

Response: "None"
Action: If there is no response within one second then the reader terminates transmission with an error buzzer. See figure 2.06.

File:HandshakingACKNAK.svg

6. ACK/NAK no response:
The difference from the ACK/NAK mode is that when no response from the host is received within 100 ms, the reader assumes that the data has been received correctly by the host.

Response: "ACK" (ASCII: Hex 06)
Action: The reader completes transmission with the good-read buzzer.

Response: "NAK" (ASCII: Hex 15)
Action: The reader sends the data again.

Response: "DC1" (ASCII: Hex 11)
Action: The reader completes transmission without a good-read or error buzzer.

Response: "None"
Action: If there is no response within 100 ms then the reader terminates transmission with a good read buzzer. See figure 2.07.

File:HandshakingACKNAKnoresponse.svg

SET Image:MenulabelZZ.png
No handshake P0 File:Menulabel P0.png
Busy/ready P1 File:Menulabel P1.png
Modem P2 File:Menulabel P2.png
XON/XOFF ZG File:Menulabel ZG.png
ACK/NAK P3 File:Menulabel P3.png
ACK/NAK/NO RESPONSE P4 File:Menulabel P4.png
Flow control Time out indefinitely I0 File:Menulabel I0.png
Flow control Time out 100 ms I1 File:Menulabel I1.png
Flow control Time out 200 ms I2 File:Menulabel I2.png
Flow control Time out 400 ms I3 File:Menulabel I3.png
END Image:MenulabelZZ.png
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