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
18
Pushbutton Switches
Two push button switches provide momentary, active-low input, for user applications. Pull-ups
internal to the MCU must be enabled to provide error-free switch operation. Pushbutton
switches SW1 and SW2 are connected to MCU I/O ports IRQ7* and IRQ1* respectively.
User LED’s
Four green LED’s are provided for use in application development and debug. Each LED is
configured for active-high operation. An LED_EN option header enables indicators LED1
through LED4. A 3S buffer between the MCU port and the user LED’s provides the drive cur-
rent necessary to control the LED’s.
Figure 11: LED_EN Option Header
LED_EN
▪
▪
ON
User LED’s enabled active-high
LED_EN
▪
▪
OFF
User LED’s disabled
Potentiometer
A 5k ohm, single-turn, thumb-wheel type, potentiometer at RV1 provides continuous, variable
resistance input for user applications. The output is the result of a voltage divider that changes
as the thumb-wheel is turned. The potentiometer is connected between VDD and GND with
the center tap providing the divider output. This center tap is connected to the MCU on input
AN0. The potentiometer may be disconnected from AN0 by means of the POT_EN option
header.
Figure 12: POT_EN Option Header
▪
▪
ON
User POT enabled
POT_EN
▪
▪
OFF
User POT disabled
POT_EN
I/O PORT CONNECTOR
Connector J1 provides access to M52221DEMO I/O signals. Signal positions not shown are
not connected (NC).
