Hitachi EH-150 Series Applications Manual page 93

 I/O mapping function
The I/O mapping function was supported from software ver. 2.0.
If an I/O mapping function is used, arbitrary I/O classification and addresses can be assigned to the address to
H0000 - HFFFF. (The table after address translation is called mapping table.)
Two mapping tables (for bits, for words) can be set up.
Coil
Input
Holding
Register
Input
Register
« Note »
Be careful of the following point at the time of I/O mapping functional use.
 The function codes 01 (Read Coil Status) and 02 (Read Input Status) turn into a code of the same purpose.
 The function codes 03 (Read Holding Registers) and 04 (Read Input Registers) turn into a code of the same
purpose.
 An input (Input) and an output (Coil) are intermingled in an address H0000 - HFFFF. The set to an input and a N
continuation set come be made, the data set to the input is updated by the actual input value by I/O refreshment.
 N continuation read or N continuation set cannot be performed ranging over I/O from which classification differs.
Reference : Merit / demerit of the I/O mapping
(1) Merit
Since I/O which can be accessed in function code was decided as shown in Table 6.14, EH-SIO cannot be accessed
at I/O which does not correspond to a function code.
Moreover, although the address of I/O is specified by 1-word data (H0000 - HFFFF) in a Modbus protocol, since
the number of the addresses of remote I/O of EH-150 is five, they cannot be accessed by the Modbus protocol.
These problems are solved by using an I/O mapping function.
(2) Demerit
Since I/O of two or more classifications is made intermingled in an address H0000 - HFFFF, a user needs to
manage the assigned address. A host has to send query conscious of I/O mapping.
Ex.) When WR0 is mapped in H8000  For accessing WR2000, it is specified as an address HA000.
Modbus
H0000
HFFFF
H0000
HFFFF
H0000
HFFFF
H0000
HFFFF
Figure 6.50 I/O mapping image
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Chapter 6 Communication Mode
EH-SIO
Mapping table
Default
H0000
Y
X
HFFFF
H0000
WR
WM
HFFFF
Bit
X
Y
R
M
Word
WR
WL
WM