Siemens LOGO! Manual page 105

Flag blocks
Flag blocks are identified by the letters M or AM . These are virtual outputs, which output the
value of their inputs. LOGO! provides 27 digital flags M1 ... M27 and 6 analog flags AM1 ...
AM6.
Startup flag
Flag M8 is set in the first cycle of the user program and can thus be used in your circuit
program as a startup flag. This signal is automatically reset after the circuit program has
completed its first cycle.
The M8 flag can be used in all further cycles for setting, deletion and evaluation procedures
in the same way as other flags.
Backlight flags M25 and M26
The M25 flag controls the backlight of the LOGO! onboard display. The M26 flag controls the
backlight of the LOGO! TD.
Note: The backlight lifetime of the LOGO! TD is 20,000 hours.
Message text character set flag M27
The M27 flag selects between the two character sets that LOGO! uses to display message
texts. State 0 corresponds to Character Set 1, and state 1 corresponds to Character Set 2. If
M27=0 (low), only message texts configured for Character Set 1 will display; If M27=1 (high),
only message texts configured for Character Set 2 will display. If you do not include M27 in
the circuit program, message texts display in the character set that you selected from either
the Msg Config menu or from LOGO!Soft Comfort.
Note
The output of the flag always carries the signal of the previous program cycle. This value
does not change within the same program cycle.
Shift register bits
LOGO! provides the shift register bits S1 to S8, which are assigned the read–only attribute in
the circuit program. The content of shift register bits can only be modified by means of the
"Shift register" (Page 191) special function.
Cursor keys
Up to four cursor keys are available to you, namely C
"Cursor"). Cursor keys are programmed for the circuit program in the same way as other
inputs. You can set the cursor keys in the corresponding display while the system is in RUN
(Page 81) , and in an active message text (ESC + Key). Cursor keys can save switches and
inputs, and allow operator control of the circuit program. Cursor key inputs from the
LOGO! TD are identical to cursor key inputs from the LOGO! Base Module.
LOGO!
Manual, 10/2017, A5E01248535-AA
LOGO! functions
4.1 Constants and connectors - Co
, C , C and C ("C" =
105