Canon SPEEDLITE 540EZ Service Manual page 35

Part 2: Technical Information
3. SWITCHES AND IC
3.1 Names of Switches and Functions
No. Symbol Name Function
1 $1 Test flash switch Test button for checking flash
2 $2 Bounce switch Switch for detecting bounce status (vertical, horizontal)
3 S3 7° downward tilt switch Switch for detecting status of 7° downward tilt
4 S4 FT/M switch Feet/meter display selector switch
5 $5 Zoom switch Zoom setting switch
6 S6 EL switch Light switch for display panel illumination
7 S7 Catchlight switch Catchlight position setting detection switch
8 S8 Wide panel switch Wide panel setting detection switch
9 sg Mode switch Flash mode selection button
10 S10 Select switch Flash strength, count, interval selection switch
114 (S11 Up switch
12 $12 Down switch
13 S13 Zoom position switch Zoom position detection switch
14 S14 Main switch Main switch
3.2 IC Functions
No. Symbol
1 IC-1
2 1IC-3
3 IC-5
4 1C-6
5 IC-7
6 IC-8
7 1IC-9
Function
Regulator IC: Generates VDD (5V) when battery is turned on, and inputs VDD to
IC3 and IC8.
Voltage detection IC: Outputs the same voltage as the input voltage when input is
3V or more. Voltage becomes OV when input is less than 3V. Used as reset for IC8
(MPU).
Regulator IC: Generated the reference voltage for the A/D converter in IC8 (MPU).
Photosensor control IC: Catches the photosensor output of the flash during
manual flash or the reflected light during pre-flash.
VF IC
MPU IC: Overall control
Zoom motor control IC