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5Application Precautions
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• Do not touch the cold junction compensator. Doing so may result in incor-
rect temperature measurement.
Caution Always clear memory before beginning to program the CPM1A. Although
memory is cleared before the CPU Unit is shipped (except for bits with specific
functions), AR 1314, which turns ON when the internal capacitor cannot back up
memory, may have turned ON during shipment.
Caution If the CPM1A will be turned off for periods exceeding the data backup period of
the internal capacitor, design the system so that it will not be influenced if data in
the DM, HR, and CNT areas is cleared when power is turned off.
Caution Either switch the CPM1A to RUN or MONITOR mode, or turn off and on power to
the CPM1A after changing from a Programming Device any data that is backed
up in flash memory. This data includes the user program, read-only DM area
(DM 6144 to DM 6599), and the PC Setup (DM 6600 to DM 6655).
• The user program and memory area data in the CPM1A are backed up either
by an internal capacitor or in flash memory as shown in the following table.
Backup method Data
Internal capacitor Read/write DM area (DM 0000 to DM 0999, DM 1022, and
DM 1023)
Error log area (DM 1000 to DM 1021)
HR area (HR 00 to HR 19)
Counter area (CNT 000 to CNT 127)
Flash memory User program
Read-only DM area (DM 6144 to DM 6599)
PC Setup (DM 6600 to DM 6655)
Note 1. The IR, TR, LR, and timer areas are not normally backed up when power is
turned off and all contents will be cleared the next time power is turned on.
(The PC Setup setting in DM 6601 can be used to back up this data. Refer to
details on the PC Setup later in this manual for details.)
2. The bits in the AR and SR areas have special functions and are set accord-
ing to these functions when power is turned on.
• The capacitor backup time depends on the ambient temperature, as shown in
the following graph. The backup time, however, assumes that the capacitor is
fully charged, which requires that power be supplied to the CPU Unit continu-
ously for at least 15 minutes.
Backup time (days)
Ambient temperature (C)
20
10
7
1
25 40 80
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