For data communication with a software handshake, “XON” must be sent
by a device when it is turned on in order to enable another on-line device to
exchange data.
Sequence:
Balance
Receiving device
– – – – – byte – – – –
→
– – – – – byte – – – –
→
– – – – – byte – – – –
→
– –
←
– – – <XOFF> – – – – –
– – – – – byte – – – –
→
(Once <XOFF> has been transmitted, a maximum
– – – – – byte – – – –
→
of 14 bytes can still be received.)
:
:
:
Pause
:
:
:
:
:
– –
←
– – – <XON> – – – – – –
– – – – – byte – – – –
→
– – – – – byte – – – –
→
Transmitting device:
The importance of handshake control for data transmission becomes
especially apparent
– when the continuous automatic data output parameter is defined
– when data output is controlled by application programs
Once <XOFF> has been received, it prevents further transmission of characters.
When <XON> is received, it re-enables the transmitting device to send data.
The transmitting device is always enabled for sending data after it has been
switched on.
If data transmission is interrupted by the control line (CTS) or the command
<XOFF> while a data block is being output from an application program (only for
printing a section of text with several lines of data), the readout will be locked
into the display at the same time.
Data output will be blocked until the interface receives an enabling signal.
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