ICP DAS USA ET-7000 Series User Manual page 138

Appendix D: Modbus Application Notes


Safe Value
If the time of the Host PC losing Modbus/TCP communication with the module is greater than
the host WatchDog timer setting (called WDT timeout), the output of the Digital and Analog
channels is set to the Safe Value, and the count of the host WDT events is increased by one.
AO address 40558 is the address of the Host WDT events. The value of the WDT events will
be not stored into EEPROM, and will return to 0 after the module is rebooted. DO address
00515 is the first address of the Safe value and the total number of channels depends on the
type of module.
For example:
Address 00515 to 00518 records the Safe value for the 4-Channel ET-7017.
Be careful to set the ON value to DO address 00432 to write the DO Safe value to the
EEPROM of the ET-7000 DO module after using Modbus commands (05 or 15) to change the
Power ON value.
While the WDT timeout is set, the module can also receive the Modbus/TCP commands (05,
06, 15 and 16) to change the DO or AO value without needing to clear the host watchdog
timeout value.
Configuration via the Web page
Browse to the homepage of the ET-7000, and click the "Modbus I/O Settings" link in the
Configuration Section of the Main Menu tree.
Click the ON/OFF radio box to set the Safe value and then click the button to
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ET-7000 AIO User Manual, Apr. 2009, V1.04, EMH-011-104
138