B&B Electronics GW-7552 - Manual - Manual (Page 34)

GW-7552 PROFIBUS/MODBUS GATEWAY User Manual (Version 1.40, Apr/2012) PAGE: 34
When GW-7552 acts as a Modbus slave (Modbus Type=Slave):
i. Data exchange between Profibus master and GW-7552 is interrupted
“I/O Safe Mode” will be activated when the data exchange between
Profibus master and GW-7552 is interrupted.
• I/O safe mode = “Switch Safe Value”
The GW-7552 will set internal DIO and AIO data to safe value.
• I/O safe mode = “Retain Last Value”
Internal DIO and AIO data retain last value
ii. Connection between Modbus master and the GW-7552 is interrupted
Internal DIO and AIO data retain last value received
Please refer section 5.4 about the safe value settings
c. Byte order is an important factor related to the memory allocation.
Big-endian byte order (Motorola format) allocates more significant
byte in lower memory address. On the other hand, little-endian byte
order (Intel format) allocates more significant byte in higher memory
address.
d. When Output Data Mode is “Auto”, the GW-7552 will update the
value of the output and input module automatically. When Output
Data Mode is “Manual”, the GW-7553 will update the value of the
input module automatically and the user must update manually the
value of the output module (please refer to section 4.6.2 Data Output
Command).
e. Modbus device ID is a Modbus address of the GW-7552, when the
GW-7552 acts as a Modbus slave device.
f. We recommend the user to set the “query message timeout value”
bigger than 3ms in order to identify the response message.
g. (M) means the parameter is effective, when Modbus type of GW-
7552 is master.
(S) means the parameter is effective, when Modbus type of GW-7552
is slave.
4.4 The Configuration of the modules
The user can set the number and size of the I/O modules in the PROFIBUS
configuration tool. The settings of the modules are described below.