M 5 2 2 2 1 D E M O U S E R G U I D E
J A N U A R Y 1 8 , 2 0 0 7
14
Due to current limitations of the USB bus when powered from the USB BDM, the ILIM option
header must be set to the LO position. Setting the ILIM option header to HI requires applying
power to the board externally.
Figure 7: ILIM Option Header
ILIM
HI
LO
● ●
Sets output current limit to 500mA. This option should only be selected when the
board is power externally.
ILIM
HI
LO
● ● ●
Sets output current limit to 100mA. This option may be selected when the board
is powered from the USB BDM or if powered externally.
A charge-pump located at U6 generates a +5V output for use when the board is power from
the USB BDM. The USB BDM provides the +3.3V rail necessary to power on-board logic but
does not provide the +5V rail necessary for USB OTG functionality. The 5V_SEL option
header selects the power source for the +5V rail.
Figure 8: 5V_SEL Option Header
●
CP
Selects output of charge-pump at U6
●
●
VR1
5V_SEL
●
CP
Selects output of voltage regulator at VR2
●
●
VR1
5V_SEL
NOTE:
The VR1 label at the 5V_SEL option header is incorrect and should read VR2. This
option selects the output of the +5V regulator at VR2.
RESET
The M52221DEMO provides a RESET button, with indicator, to reset the target device. The
MCF52221 also supports several internal resets. Consult the MCF522235 RM for details on all
supported resets.
RESET SWITCH
The RESET switch provides a method to apply an asynchronous reset to the MCU and is con-
nected directly to the RSTI* input on the MCU. Pressing the RESET switch holds RSTI* low
until the switch is released. An external pull-up on the RSTI* line prevents spurious resets al-
lowing normal operation.
