ICP DAS USA GW-7552-B User Manual page 35

Internal DIO and AIO data retain last value
When GW-7552-B / GW-7552-M acts as a Modbus slave (Modbus
Type=Slave):
i. Data exchange between Profibus master and GW-7552-B / GW-7552-M
is interrupted
"I/O Safe Mode" will be activated when the data exchange between
Profibus master and GW-7552-B / GW-7552-M is interrupted.
 I/O safe mode = "Switch Safe Value"
The GW-7552-B / GW-7552-M 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-B / GW-7552-M
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-B / GW-7552-M
will update the value of the output and input module automatically.
When Output Data Mode is "Manual", the GW-7552-B/GW-7552-M
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-B / GW-
7552-M, when the GW-7552-B / GW-7552-M 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-B / GW-7552-M is master.
(S) means the parameter is effective, when Modbus type of GW-
GW-7552-B / GW-7552-M PROFIBUS/MODBUS GATEWAY User Manual (Version 1.60, May/2017) PAGE: 35