Reset
Demonstration Board for Freescale MCF5211, Rev. 1
Freescale Semiconductor
11
Consider the maximum output current of the selected power source when attempting to power off-board
circuitry through connector J1.
7.4.2
VX_EN
The VX_EN option header is a two-pin jumper that connects the target-board voltage rail to J1-1. J1-3 is
connected directly to the ground plane. Use of this input requires a reg3.3 V voltage source. This
power input is decoupled to minimize noise input but is not regulated. Also, no protection is applied on
this input and damage to the target board may result if over-driven. Do not attempt to power the target
board through this connector while applying power through the USB-BDM or the PWR connector;
damage to the board may result.
Power may be sourced to off-board circuitry through the J1 connector. The current limitation of the USB
bus or the on-board regulator must be considered when attempting to source power to external circuitry.
Excessive current drain may damage the target board, the host PC USB hub, or the on-board regulator.
details the VX_EN option header connections.
Figure 7. VX_EN Option Header
CAUTION
Do not apply power to connector J1 while sourcing power from either the
PWR connector or the USB-BDM circuit. Damage to the board may result.
NOTE
Do not exceed available current supply from USB-BDM cable or on-board
regulator when sourcing power through connector J1 to external circuitry.
8
Reset
The MCF5211 can be reset several ways. A RESET switch applies an external reset to the device. An
internal low-voltage detect forces the part into RESET when voltage falls too low. The part may also be
reset by applying a logic low on the RSTI* signal. The RSTI* signal is used by a connected BDM to force
the part into reset when necessary. A reset indicator shows when the part is in reset.
8.1
Reset Switch
The RESET switch provides a method to apply an asynchronous reset to the MCU and is connected
directly to the RSTI* input on the MCU. Pressing the RESET switch forces the MCU into reset until the
Enable power connection to connector J1
VX_EN
Disable power connection to connector J1
ON
VX_EN
OFF
