B&B Electronics GW-7553 - Manual - Manual (Page 31)

GW-7553 PROFIBUS/Modbus TCP Gateway User Manual (Version 1.00, Dec/2008) PAGE: 31
When GW-7553 acts as a Modbus Slave (Modbus Type=Slave):
i. Data exchange between PROFIBUS Master and GW-7553 is interrupted
“I/O Safe Mode” will be activated when the data exchange between
PROFIBUS Master and GW-7553 is interrupted.
• I/O safe mode = “Switch Safe Value”
The GW-7553 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-7553 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. Modbus device ID is a Modbus address of the GW-7553, when the GW-7553
acts as a Modbus Slave device.
e. We recommend the user to set the “query message timeout value” bigger than
3ms in order to identify the response message.
f. The user can set the maximum number of Modbus TCP Slave device by
“TCP_Connect_Num”. These Modbus TCP Slave devices can have different
IP Address for connection.
g. (M) means the parameter is effective, when Modbus Type of GW-7553 is
Master.
(S) means the parameter is effective, when Modbus Type of GW-7553 is
Slave.
(T) means the parameter is effective, when Modbus Format of GW-7553 is
TCP.
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.
●
Max. I/O modules：32 modules
●
System setting module：3 byte out
●
Output module：Output Relay/Coil => 1~32 Bytes
Output Register => 1~64 Words