CPU_45A-V3
CPU Board XMC4500 General Purpose
Hardware Description
Board User's Manual
12
Revision 1.0, 2014-01-10
2.2
Reset
The reset pin (PORST#) of the XMC45000 is a bi-directional pin. An internal pull-up resistor will keep the
PORST# pin high during normal operation. A low level at this pin will force a hardware reset. In case of an
internal reset the PORST# pin will drive a low signal. An internal circuit of the XMC4500 ensures a save Power-
on-Reset. XMC4500 does not require any additional external components to generate a reset signal during
power-up. An on-board reset button (SW400, RESET) supports a hardware reset of the CPU during operation.
The reset signal is also routed to all satellite connectors. The reset state is indicated by a red LED (V407). The
LED
will be “ON” during reset state and will be “OFF” during normal operation conditions.
Figure 6
Reset
Reset Button
Reset LED
RST.emf
Figure 7
Reset LED and Reset Switch
2.3
Clock Generation
An external 12 MHz crystal provides the clock signal to the XMC4500 microcontroller. The drive strength of the
oscillator is set to maximum by software, in order to ensure a safe start-up of the oscillator even under worst
case conditions. A serial 510 Ohm resistor will attenuate the oscillations during operations.
For the RTC clock a separate external 32.768 kHz crystal is used on board.
