Freescale Semiconductor S08 User Options, Pushbutton Switches, LED Indicators, ADC Interface

Hardware Description

2.9 User Options

The DEMO9S08AW60LED includes various input and output devices to assist in application development. These devices include four pushbutton switches, four LEDs, and an operational amplifier with RC filter connected at each ADC input channel for signal amplification and filtering.

2.9.1 Pushbutton Switches

Four pushbutton switches provide momentary active low input for user applications. The table below describes the pushbutton switch connections.

Table 2-3. Pushbutton Switches (SW1-SW4) Connections

Switch	MCU Port
SW1	PTG0/KBI0
SW2	PTG1/KBI1
SW3	PTG2/KBI2
SW4	PTG3/KBI3

2.9.2 LED Indicators

Four green LED indicators (D1-D4) are provided to assist during code development. The LEDs are active low and illuminated when a logic low signal is driven from the MCU port pin. Two of the LEDs are connected to port A, and the other two are connected to Port C. The connections are described below:

Table 2-4. LEDs (D1-D4) Connections

LED	MCU Port
D1	PTA0
D2	PTA1
D3	PTC2
D4	PTC4

2.9.3 ADC Interface

Eight operational amplifiers are provided to assist users in developing applications with feedback control signals. For examples, the signal generated by an optical sensor in LED backlight system should be scaled to a level matched with the ADC input range without any saturation. Each operational amplifier can be configured as an inverting or non-inverting amplifier with variable gain setting by different resistor connections. A RC filter is also connected at each output for noise filtering.

NOTE

The maximum operational amplifier output voltage should be limited to the

VDD voltage applied to MCU to prevent any damage on input port.

LED Lighting Control using the MC9S08AW60, Rev. 1

14 Freescale Semiconductor