Mecablitz 44Mz; Sca Interface - Metz mecablitz 44 MZ-2 Servicehandbuch

Technik und Service Seite: 38
Technology and Service Page: 38
mecablitz 44 MZ-2 / 44 AF-3
ENGLISH

6. mecablitz 44MZ-2:

6.1. SCA interface:

The SCA interface of the mecablitz is designed such that the flashgun can be used with adapters of the
SCA 3002 and SCA 300 systems. It cannot be used with adapters of the SCA 3000 system!
SCA 1 - Ground:
The contact SCA 1 is the ground connection between the mecablitz and the SCA adapter.
SCA 2- AF measuring beam:
In order to activate the red-light emitter in the mecablitz, an SCA 3002 adapter connects contact SCA 2 to
ground via a transistor (SCA 2 = LOW). This activates the red-light emitter D001 on the printed circuit board
G.
SCA 3 - Data-bus identification:
The mecablitz is capable of exchanging data with an SCA adapter of the SCA 3002 system via a digital data
bus (SCA 11 and SCA 12). In order to inform the SCA adapter that the flashgun has this capability, the µC
IC401 switches Pin 31 to LOW when the mecablitz is switched on. This cuts off Tr415. From this, and from its
internal circuitry for contact SCA 3, the SCA adapter recognises that the mecablitz is a data-capable flashgun.
If there is any status change in the mecablitz which needs to be signalled to the SCA adapter (such as reaching
the flash-ready state), an exchange of data via the data bus must be initiated. For the exchange of data
between the mecablitz and the SCA adapter, the SCA adapter acts as the master, which means that it also
provides the CLOCK signal. In order to request the master to start a data exchange, the mecablitz switches
Pin 31 (NSBB Request) of its µC IC401 to HIGH. After inversion by transistor Tr415, this request is then
available as a LOW level at contact SCA 3. The SCA adapter then starts the data exchange (via SCA 11 and
SCA 12). At about the time when the first data bus packet is received, Pin 31 of IC401 returns to LOW and
contact SCA 3 thus returns to HIGH.
SCA 4 - Exposure verification:
If, in automatic flash mode or TTL flash mode, the flash was sufficient for correct exposure, µC IC401 briefly
switches Pin 34 (LED OK) from HIGH to LOW. This causes Tr428 to cut off and the base of Tr408 receives a
drive voltage via R4033 and R4099. Tr408 conducts. The base of Tr407 is connected to ground via R4032.
Tr407 therefore also conducts and a HIGH level appears at contact SCA 4 for about 3 seconds. This is the OK
signal for the SCA adapter.
Contact SCA 4 is used only by adapters of the SCA 300 system. The adapters of the SCA 3002 also receive
the status of the exposure verification indicator via the data bus (SCA 11 and SCA 12) and evaluate only this
signal.