Technik und Service
Seite: 40
Technology and Service
Page: 40
mecablitz 44 MZ-2 / 44 AF-3
ENGLISH
SCA 9 - Auxiliary voltage for TTL with SCA 300:
Contact SCA 9 carries an auxiliary voltage for the TTL flash mode with adapters of the SCA 300 system. This
voltage is derived from the switched 5 V supply voltage at the collector of Tr406. In standby mode of the
mecablitz, this voltage is switched off by Tr406.
In order to terminate a TTL flash, the SCA 300 adapter connects this voltage back to contact SCA 7. The
contact SCA 9 has no function for adapters of the SCA 3002 system.
SCA 10 - SYN trigger:
In order to trigger a flash, the SCA adapter connects contact SCA 10 (SYN) to ground (LOW). The base of
transistor Tr418 is driven via D4055 and R4054 and the collector-emitter path of Tr418 conducts. The base of
Tr417 is thus driven via R4051, Tr417 conducts and its collector switches Pin 52 (SYN IN) of the IC401 to
ground (LOW). For the µC IC401, this is the signal to trigger a flash (providing the mecablitz is ready for
firing).
SCA 11 and SCA 12 - Data bus:
Data are exchanged between the mecablitz and the SCA 3002 adapter via the contacts SCA 11 (DATA
IN/OUT) and SCA 12 (CLOCK). The SCA adapter acts as the master, the mecablitz as the slave.
The CLOCK signal from the SCA adapter is evaluated at Pin 51 (NSBB INTR) of IC401. The data for the SCA
adapter are output at Pin 33 (NSBB DO); the data from the SCA adapter arrive at Pin 32 (NSBB DI).
Before a data exchange is started, both of the contacts SCA 11 and SCA 12 are LOW. In order to start the
data exchange, the adapter switches both contacts SCA 11 and SCA 12 to HIGH. Transistor Tr412 conducts
and its collector switches to LOW, which means that Pin 51 (NSBB INTR) of the µC IC401 is also LOW. This
LOW generates an interrupt in the µC. The µC thus recognises that the data exchange has started and
switches Pin 33 (NSBB DO) to HIGH. The base of Tr414 is driven and Tr414 conducts. The potential on
SCA 11 is pulled down to LOW by Tr414. The SCA adapter detects this and switches contact SCA 12 to LOW.
Tr412 cuts off and Pin 51 (NSBB INTR) of the µC IC401 switches to HIGH. Pin 33 (NSBB DO) switches to
LOW, Tr414 cuts off and SCA 11 returns to HIGH. The first data bit is then transmitted on the data bus with
the next LOW-HIGH transition on SCA 12 (CLOCK) and the µC evaluates the level on SCA 11 to detect it.
SCA 13 - Supply voltage for SCA 3002:
This voltage is the supply voltage for the adapters of the SCA 3002 system. It is taken from the battery voltage
and protected against overloads by R301 and fuse Si301.
SCA 14 - IGBT control:
The mecablitz 44 MZ-2 does not support the direct control of the IGBT Tr401 by the SCA adapter. For this
reason, contact SCA 14 is not connected.
