Conrad C-Control Pro Mega Series, Manual, Page: 32 / 240

23 C-Control Pro Mega Series
© 2008 Conrad Electronic
74HC165 holds only 8 Bit information, Q7 of the 1st 74HC165 is connected with DS of the 2nd
74HC165.
I2C Interface
Through this interface serial data can be transmitted at high speed. To do this only two signal lines
are necessary. Data transmission takes place according to the I2C protocol. To effectively use this
interface special functions are provided (see Software Description I2C).
I2C SCL I2C Bus Clock Line PortC.0
I2C SDA I2C Bus Data Line PortC.1
Power Supply (POWER, 5 Volts, GND)
Power is provided to the application board by means of a 9V/ 250mA Mains Plug-in Power Supply.
Depending on additionally used components it may later become necessary to use a power supply
with higher power rating. A fixed voltage control generates an internally stabilized 5V supply voltage.
This voltage is provided to all circuit components on the application board. Due to the power reserve
of the Plug-In Power Supply this voltage can also be used to power external ICs.
Please observe the Maximum Drawable Current . Exceeding this current may lead to immediate
destruction! Because of the relativelly high current consumption of the application board in the
vicinity of 125mA it is not recommended for use in devices consistently battery operated. Please see
the note on short time breakdowns of the power supply (see
Reset Characteristics ).
If you turn the application board to a position where the interface connectors (USB and serial)
show to the upper side, the leftmost column on the breadboard is GND and the rightmost column is
VCC.
Serial Interfaces
The Micro Controller Atmega32 contains in its hardware an asynchronous serial interface according
to RS232 standards. The format (Data Bits, Parity Bit, Stop Bit) can be determined during
initialization of the interface. The application board contains a high value level conversion IC to
transform the digital bit streams to Non Return Zero Signals in accordance with the RS232
standards (positive voltage for low bits, negative voltage for high bits). The level conversion IC makes
use of an improved protection against voltage transients. Voltage transients can in electro-
magnetically loaded surroundings (e. g. in industrial applications) be induced in the interface cables
and thus destroy connected electrical circuits. By means of jumpers the data lines RxD and TxD
can be connected to the Controller PortD.0 and PortD.1. During quiescent condition (no active data
transmission) a negative voltage of several volts can be measured on Pin TxD against GND. RxD is
of high impedance. The 9 pole SUB-D socket of the application board carries RxD on Pin 3 and TxD
on Pin 2. Pin 5 is the GND connection. No handshake signals are being used for serial data
transmission.