Technical data

170 • MODBUS Functions
Internal Variables
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
6.5.5 Constant Registers
The following registers contain constants, which can be used to test
communication with the master:
Register address 0x2000 (MODBUS Address 408193)
Value Zero, GP_ZERO
Access Read
Description Constant with zeros
Register address 0x2001 (MODBUS Address 408194)
Value Ones, GP_ONES
Access Read
Description Constant with ones. Is –1 if this is declared as "signed int" or MAXVALUE i
f
it is declared as "unsigned int".
Register address 0x2002 (MODBUS Address 408195)
Value 1,2,3,4, GP_1234
Access Read
Description This constant value is used to test the Intel/Motorola format specifier. If the
master reads a value of 0x1234, then with Intel format is selected – this is the
correct format. If 0x3412 apears, Motorola format is selected.
Register address 0x2003 (MODBUS Address 408196)
Value Mask 1, GP_AAAA
Access Read
Description This constant is used to verify that all bits are accessible to the fieldbus
master. This will be used together with register 0x2004.
Register address 0x2004 (MODBUS Address 408197)
Value Mask 1, GP_5555
Access Read
Description This constant is used to verify that all bits are accessible to the fieldbus
master. This will be used together with register 0x2003.
Register address 0x2005 (MODBUS Address 408198)
Value Maximum positiv number, GP_MAX_POS
Access Read
Description Constant in order to control arithmetic.
Register address 0x2006 (MODBUS Address 408199)
Value Maximum negativ number, GP_MAX_NEG
Access Read
Description Constant in order to control arithmetic.
Register address 0x2007 (MODBUS Address 408200)
Value Maximum half positiv number, GP_HALF_POS
Access Read
Description Constant in order to control arithmetic.
Register address 0x2008 (MODBUS Address 408201)
Value Maximum half negativ number, GP_HALF_NEG
Access Read
Description Constant in order to control arithmetic.