Internal Relays M And F, Latch Relay L; Special Relays Sm - Mitsubishi Electric MELDAS 60 Series Programming Manual

5.3.2 Internal Relays M and F, Latch Relay L

The internal relay and latch relay are auxiliary relays in the PLC that cannot directly output to an
external source.
Internal relays M
(a) These relays are cleared when the power is turned OFF.
(b) There is no limit to the No. of "A" contacts and "B" contacts of the internal relays that can be
used in the program.
(c) The internal relay No. is expressed with a decimal.
Internal relay F
Internal relay F is an interface for the alarm message display.
Use the bit selection parameter to determine whether to use this relay for the alarm message
interface. The target will be F0 to F127. This internal relay can be used in the same manner as the
internal relay M when not used as the alarm message interface.
Latch relay L
(a) The original state is held even when the power is turned OFF.
(b) There is no limit to the No. of "A" contacts and "B" contacts of the latch relay that can be used
in the program.
(c) The latch No. is expressed with a decimal.

5.3.3 Special Relays SM

The special relays are relays having fixed applications such as the carrier flag for operation results
and the display request signal to the setting and display unit. Even the relays of SM0 to SM127 that
are not currently used must not be used as temporary memory.
Special relays SM
(a) This relay is cleared when the power is turned OFF.
(b) There is no limit to the No. of "A" contacts and "B" contacts of the special relays that can be
used in the program.
(c) The special relay No. is expressed with a decimal.
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5. Explanation of Devices