Technik und Service
Seite: 49
Technology and Service
Page: 49
mecablitz 44 MZ-2 / 44 AF-3
ENGLISH
When flash exposure was sufficient, the camera switches SK2 to ground (TTL pulse). After inversion by Tr414,
this results in a HIGH level at pin 13 of IC406D. Since both inputs (pins 12 and 13) of the NAND gate
IC406D are now HIGH, its output (pin 11) changes to LOW and the output (pin 10) of the following NAND
gate IC406C changes from LOW to HIGH. The following inversion by IC406B results in a LOW output level
on pin 4. The IGBT cuts off and the flash is terminated.
Data bus:
Data are exchanged between the mecablitz and the camera on two wires. The CLOCK signal of the data bus
is transmitted via SK1, the data signal via SK2.
CLOCK on SK1:
When transmitting data to the mecablitz, the camera generates the CLOCK signal on SK1. The alternating
levels on SK1 cause Tr412 to conduct (SK1 HIGH) and to cut off (SK1 LOW). The CLOCK signal from the
camera is thus inverted and is available at pin 50 (CSC CAMERA CLOCK) of the µC IC401.When transmitting
data to the camera, the mecablitz generates the CLOCK signal. The CLOCK signal comes from pin 36 (BG-
CLOCK SCC) of the µC IC401 and drives Tr411. The signal from pin 36 is inverted and is available to the
camera at SK1 (collector of Tr411).
Data on SK2:
For data transfer from the mecablitz to the camera, the data signal comes from pin 31 (DATA_OUT) of the µC
IC401. The signal from pin 31 is inverted and is available at the collector of Tr413 or at SK2 for transmission
to the camera. For data transfer from the camera to the mecablitz, the µC switches pin 31 to LOW, cutting off
Tr413. The incoming data signal from the camera drives Tr414 via D403.
Special contact SK3
In order to start a data transfer between the camera and the mecablitz, the camera must switch SK3 to LOW
or ground. In manual flash mode M or Mlo, the µC IC401 switches pin 58 (Mode) to LOW. Tr424 cuts off.
The camera provides a voltage on SK3, and this settles to about 1.6 V in manual flash mode. In TTL flash
mode, the µC IC401 switches pin 58 (Mode) to HIGH. Tr424 conducts and an additional load (R4058) is
connected to SK3, causing the voltage there to drop.
Wake-up by the camera
If the mecablitz has been switched to standby mode by its "Auto-Off" function, it can be switched on again by
lightly touching the camera's shutter release button.
The comparator IC403A which monitors the special contact SK3 is connected to the +5.0V supply voltage
(which remains on in standby mode). When the user touches the shutter release button the camera sends a
voltage to the camera on SK3. This signal is detected by the comparator IC403A, which causes the voltage at
the interrupt input at pin 51 (CLK/TTL) of the µC IC401 to change from LOW to HIGH. The µC then switches
the mecablitz on again.
