Program Memory And Devices; Memory Structure - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
2.6

Program Memory and Devices

2.6.1

Memory structure

1. In FX /FX
3U 3UC
FX /FX PLCs are equipped with the RAM memory as standard.
3U 3UC
By mounting a memory cassette, the memory type can be changed.
1) When using the built-in memory (without attached memory cassette)
Built-in device memory (RAM)
Contact image memory
• Input relay (X)
• Auxiliary relay (M) • State relay (S)
Timer contact and time counting coil
Counter contact, counting coil, and reset coil
Built-in program memory
Parameter
Sequence program
Comment
File register (D)
2) When using an attached memory cassette (without using the built-in program memory)
Built-in device memory (RAM)
Contact image memory
• Input relay (X)
• Auxiliary relay (M) • State relay (S)
Timer contact and time counting coil
Counter contact, counting coil, and reset coil
Built-in program memory
Not used
The PLC automatically recognizes attachment of a
memory cassette (when the power is turned ON),
and disconnects the built-on program memory.
(The priority is given to the memory cassette.)
34
PLCs
CPU
[Bit device memory]
• Output relay (Y)
(RAM)
CPU
[Bit device memory]
• Output relay (Y)
(RAM)
2 Overview (Sequence Program)
2.6 Program Memory and Devices
System ROM
[Data memory]
• Data register (D)
• Timer present value register (T)
• Counter present value register (C)
• Index register (V, Z)
• Extension register (R)
Memory cassette
(Flash memory)
Not attached
System ROM
[Data memory]
• Data register (D)
• Timer present value register (T)
• Counter present value register (C)
• Index register (V, Z)
• Extension register (R)
Memory cassette
(Flash memory)
Parameter
Sequence program
Comment
File register (D)
Extension file register (ER)