Mitsubishi MELSEC System Q Manual page 151

More Advanced Programming
Special function module address
Since you can attach multiple special function modules to a base unit each module needs to
have a unique identifier so that you can address it to transfer data to and from it. This identifier
results from the slot where the module is installed respectively from the I/O numbers occupied
by the digital inputs and outputs of the special function module (see chapter 3.2.2).
Crucial is the head address of the special function module. For example, if a special function
module occupies the range from X/Y010 to Y/X01F the head address is X/Y010. For a FROM
or TO instruction however the least significant digit is omitted and the head address in this case
reads as "1". When the special function module occupies the range from X/Y040 to Y/X04F, the
head address will be "4".
Starting address in the buffer memory
Every single one of the 32,767 buffer addresses can be addressed directly in decimal notation
in the range from 0 – 32,767. When you access 32-bit data you need to know that the memory
cell with the lower address stores the less significant 16 bits and the cell with the higher
address stores the more significant bits.
This means that the starting address for 32-bit data is always the address containing the less
significant 16 bits of the double word.
Number of data units to be transferred
The quantity of data is defined by the number of data units to be transferred. When you execute
a FROM or TO instruction as a 16-bit instruction this parameter is the number of words to be
transferred. In the case of the 32-bit versions DFROM and DTO the parameter specifies the
number of double words to be transferred.
16-bit instruction
Units of data: 5
D100
D101
D102
D103
D104
Data destination or source in the PLC CPU
In most cases you will read data from registers and write it to a special function module, or copy
data from the module's buffer to data registers in the PLC CPU. However, you can also use out-
puts, relays and the current values of timers and counters as data sources and destinations.
Pulse-triggered execution of the instructions
If you add a P suffix to the instructions the data transfer is initiated by pulse trigger (for details
see the description of the MOV instruction in section 6.2.1).
MELSEC System Q Beginners Manual
Buffer address n+1
More significant 16 bits
Adr. 5
Adr. 6
Adr. 7
Adr. 8
Adr. 9
Instructions for Moving Data
Buffer address n
Less significant 16 bits
32-bit data
32-bit instruction
Units of data: 2
D100
D101
D102
D103
D104
Adr. 5
Adr. 6
Adr. 7
Adr. 8
Adr. 9
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