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Mode of operation of the system
Deutschmann Automation GmbH & Co. KG
18
UNIGATE fieldbus gateway for ProfibusDP V. 4.7
29.4.11
6.5
Run-up phase
The Master programs and configures the gateway in the run-up phase. Data exchange with the
external device does not occur until after the run-up phase has been completed with no errors.
6.6
The trigger byte - only at UNIGATE RS
Since the data is always transferred cyclically on Profibus, the gateway must detect when the
user wishes to send new data via the serial interface. This is normally done by the gateway com-
paring the data to be transferred via the Profibus with the old data stored internally (data
exchange on change). In many cases however, this cannot be used as the criterion, e.g. when-
ever the same data is to be sent. For this reason, the user can set control of transmission via a
trigger byte. In this mode, the gateway always sends (and only sends) when the trigger byte is
changed.
Accordingly, the application program in the control in Normal mode cannot detect whether the
gateway has received several identical telegrams. If Trigger-Byte mode is activated, the gateway
increments the trigger byte each time a telegram has been received.
The first byte in the Profibus input/output data buffer is used as the trigger byte if this mode is
activated.
6.7
The length byte - only at UNIGATE RS
The user can configure whether the transmit length is also to be stored as a byte in the input/out-
put data area. In transmit direction, as many bytes as specified in this byte are sent. On reception
of a telegram, the gateway enters the number of characters received.
Содержание UNIGATE RS232/422
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