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29.6.20
UNIGATE
®
Fieldbus Gateway UNIGATE
®
CL - MPI V. 3.1
39
Deutschmann Automation GmbH & Co. KG
Implemented protocols in UNIGATE® CL with Universal Script
10.5 Protocol „Universal Modbus ASCII Master/Slave“
The fieldbus data exchange for Modbus ASCII is identical with RTU. The UNIGATE
®
automati-
cally transmits the data in ASCII format on the serial side.
Protocol description: see chapter 8.6 "Protocol „Universal Modbus RTU Slave“" respectively see
chapter 10.4 "Protocol „Universal Modbus RTU Master“".
10.6 Protocol SSI
With the SSI protocol, e.g. SSI encoders are evaluated with the UNIGATE
®
and this information
is forwarded to the higher-level controller. Parameters can be used to configure the encoder
type, the encoder resolution, the clock frequency and an ERROR bit (if supported) according to
the SSI encoder used. See also chapter 6 (SSI-interface).
10.7 The trigger byte
In case the data records, that were supplied from the application to the gateway, do not change
for a longer period, there is actually no need to send new data to the master.
The other way round, when it comes to a cyclical query of the gateway, a connected master has
to be in the position to distinguish whether the application constantly provides identical data or if
no new data were provided by the application for a longer period. For this reason, the user can
set control of transmission via a trigger byte (data exchange
→
On Trigger). In this mode, the
gateway always sends (and only then) 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 input/output data buffer is used as the trigger byte if this mode is activated.
10.8 The length byte
The user can configure whether the transmit length is also to be stored as a byte in the input/out-
put data area (Fieldbus lengthbyte
→
active). 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.