M5211DEMO Datasheet M5211DEMO | P10-P12

Demonstration Board for Freescale MCF5211, Rev. 1

Power

Freescale Semiconductor10

7.3 Power (OFF/ON) Switch

The OFF/ON switch, shown in Figure 5, connects and disconnects all input voltage sources to the board.

In the OFF position, the board is unpowered and no voltage is present on the upper voltage rail. In the ON

position, the input voltage source is connected to the upper voltage rail.

Figure 5. OFF/ON Switch

7.4 Power Select

Configuration of applied input power is controlled using two option headers. The PWR_SEL header

selects between the on-board voltage regulator and the USB voltage input. The VX_EN header connects

J1-1 directly to the upper voltage rail. The illustrations below show the different configuration for each

option header.

7.4.1 PWR_SEL

Figure 6 shows the PWR_SEL header.

Figure 6. PWR_SEL Option Header

Power from the integrated BDM is drawn from the USB bus and is limited to 500 mA. Excessive current

drain will violate the USB specification causing the USB bus to disconnect.

CAUTION

Violating the USB specification will cause the USB bus to disconnect. This

will cause the board to reset.

The on-board voltage regulator (VR1) accepts power input through a 2.1 mm barrel connector (PWR).

Input voltage may range from +5 V to +20 V. VR1 provides a +3.3 V fixed output limited to 800 mA.

Over-temperature and over-current limit built into the voltage regulator provides limited protection from

damage due to excessive stresses.

CONFIGURATION

OFF/ON

OFF—Input power source disconnected from upper voltage rail

ON—Input power source connected to upper voltage rail

Select power input from USB-BDM

VDD

PWR_SEL

VB VDD

PWR_SEL

Select power input from VR1

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 regulated +3.3 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.

Figure 7 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

VX_EN

OFF

Demonstration Board for Freescale MCF5211, Rev. 1

Low-Power Modes

Freescale Semiconductor12

switch is released. An external pullup on the RSTI* line prevents spurious resets and allowing normal

operation.

8.2 Low-Voltage Detect

The MCF5211 utilizes an internal Low-Voltage Detect (LVD) to protect against under-voltage conditions.

The LVD is enabled out of RESET. Consult the MCF5213 Integrated Microcontroller Reference Manual

for details on configuring LVD operation.

8.3 Reset Indicator

The RESET LED turns on when the MCU is in RESET and remains on for the duration of a valid RSTO*

signal.

9 Low-Power Modes

The MCF5211 supports several operational modes designed to reduce power consumption. Low-power

modes include Wait, Doze, Stop, and Halt. Refer to the MCF5213 Microcontroller Family Hardware

Specification and the MCF5213 Integrated Microcontroller Reference Manual for details on configuring

and using the various low-power modes.

10 Timing

Timing for the M5211DEMO is provided by an on-chip, 8 MHz relaxation oscillator in default

configuration. Resistor R23 causes the MCU to select the internal oscillator as the timing source out of

reset. Refer to the M5213 Integrated Microcontroller Reference Manual for details on use and

configuration of internal timing.

Pad locations for an external crystal oscillator have been provided but not populated in default

configurations. The external oscillator is connected to the XTAL and EXTAL inputs. To implement an

external crystal oscillator simply remove R23, install the oscillator and related circuitry. The XTAL_EN

shunt must be installed to enable external timing operation.

Figure 8. OSC_EN Option Header

Pad locations for an optional 32.768 kHz have also been provided but not populated. The 32.768 kHz

timing input is connected to GPT0 and GPT1 inputs. To implement this timing input, simply install the

timing source and related circuitry.

Enables external crystal oscillator input to MCU

XTAL_EN

Disables external crystal oscillator input to MCU

XTAL_EN

OFF

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M5211DEMO

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