300 • Common MODBUS functions
General Registers
Modular I/O System
ETHERNET TCP/IP
6.2.16 General
Registers
The following registers contain constants which can be used to test the commu-
nication with the master:
Register address 0x2000
Designation
Zero, GP_ZERO
Access
Read
Description
Constant with zero
Register address 0x2001
Designation
Ones, GP_ONES
Access
Read
Description
Constant with ones. Is –1 if this is declared as "signed int" or MAXVALUE
with "unsigned int"
Register address 0x2002
Designation
1,2,3,4, GP_1234
Access
Read
Description
Constant value to test whether High and Low byte is changed over (In-
tel/Motorola format). Should appear in master as 0x1234. If 0x3412 appears,
High and Low byte have to be changed over.
Register address 0x2003
Designation
mask 1, GP_AAAA
Access
Read
Description
Constant to check whether all bits are available. Used together with the
0x2004 register.
Register address 0x2004
Designation
mask 1, GP_5555
Access
Read
Description
Constant to check whether all bits are available. Used together with the
0x2003.
Register address 0x2005
Designation
Highest positive number, GP_MAX_POS
Access
read
Description
Constant to check the arithmetic.
Register address 0x2006
Designation
Highest negative number, GP_MAX_NEG
Access
read
Description
Constant to check the arithmetic.
Register address 0x2007
Designation
Highest half positive number, GP_HALF_POS
Access
read
Description
Constant to check the arithmetic.
Register address 0x2008
Designation
Highest half negative number, GP_HALF_NEG
Access
read
Description
Constant to check the arithmatic.