Mitsubishi Electric FX3G SERIES, Руководство по программированию

Страница: 129 / 948

127
FX
3G
/FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.9 Data Register and File Register [D]
1
Introdu
ction
2
Ov
ervi
ew
3
Instruction Li
st
4
D
evices
in Det
ail
5
Specifi
ed the
De
vice
&
C
onst
ant
6
Bef
ore Pr
og
ra
mmi
ng
7
Bas
ic Instruction
8
FN
C00-FN
C0
9
Program Fl
ow
9
FNC
10-FN
C19
Mov
e & Com
pare
10
FNC
20-FNC
29
Arith. & Lo
gi
c
Operati
on
4.9.3 Functions and operation examples of data registers
Data registers are devices for storing numeric data.
Each data register stores 16-bit data (whose most significant bit specifies the positive or negative sign). Two data
registers combined can store 32-bit numeric data (whose most significant bit specifies the positive or negative sign).
1. General type and latched (battery backed) type data registers
• Once data is written to a data register it does not change unless other data overwrite it.
When the PLC mode switches from "RUN" to "STOP" or when the power is interrupted, however, all data stored in
general type data registers is cleared to "0".
If the special auxiliary relay M8033 has been driven in advance, data is held even when the PLC mode switches
from "RUN" to "STOP".
• Latched (battery backed) type data registers hold their contents even when the PLC mode switches from "RUN" to
"STOP" or when the power is interrupted.
In FX
3U
/FX
3UC
PLCs, the contents of data registers are backed up by the battery built into the PLC.
In FX
3G
PLCs, the contents of data registers are backed up by the EEPROM built into the PLC. When the optional
battery is installed, the battery backs up the contents of some general type data registers against power failure.
The contents of data registers are backed up by the battery built in the PLC.
→
For details on each backup method, refer to Section 2.6.
• When using fixed latched (battery backed) type data registers as general type data registers, provide the following
reset circuit by RST or ZRST instruction at the head step in a program.
→
For file registers, refer to Subsection 4.8.4.
2. Special type data registers
• Special type data registers contain informative, special purpose data and are sometimes written to during program
operation.
The contents of special type data registers are cleared to their initial values when restoring the power.
(Generally, these data registers are cleared to "0" at first, and then the initial values (if there are any) are written by
the system ROM.)
• For example, the watchdog timer time is set initially to D8000 by the system ROM. When changing the contents,
write a desired time to D8000 by transfer instruction MOV (FNC 12).
→
For the data backup characteristics of special data registers, refer to Section 2.6 and Chapter 37.
→
For the types and functions of special data registers, refer to Chapter 37.
M8002
Initial pulse
FNC 40
ZRST
D512 D999
Data stored in D512 to D999 are
cleared to "0".
Ex. FX
3U
/FX
3UC
PLCs
M8002
Initial pulse
FNC 12
MOV
K250 D8000
FNC 07
WDT
The watchdog timer is set to 250 ms.
The watchdog timer is refreshed.