Advanced Parallel I/O - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 359

The signal edge to wake up the microcontroller could be rising or falling. When the rising
edge is selected, the pull-down device should be enabled. When the falling edge is chosen, the
pull-up device should be enabled. Ports H, J, and P provide the key-wake-up capability.

7.14 Exercises

E7.1 Can the AS logic family drive the HCS12 input pins? Can the HCS12 output drive the AS
logic input?
E7.2 Can the ACT logic family drive the HCS12 input? Can the HCS12 output drive the ACT
logic input?
E7.3 Can the ABT logic family drive the HCS12 input? Can the HCS12 output drive the ABT
logic input?
E7.4 Can the BCT logic family drive the ABT logic input? Can the ABT logic drive the BCT
logic input?
E7.5 For the circuit shown in Figure 4.15a, what resistor value should be used to allow 5 mA
current fl ow through the LED assuming the voltage drop across the LED is 2.1 V when it is for-
ward biased and the port pin output is 4.9 V?
E7.6 For the circuit shown in Figure 4.15a, what resistor value should be used to allow 5 mA
current fl ow through the LED assuming the voltage drop across the LED is 1.7 V when it is for-
ward biased and the port pin output is 4.8 V?
E7.7 Write an assembly and a C program to display the following information in two rows in
the LCD connected to the demo board:
Date: 10 10 1952
Time: 10:20:10
E7.8 Calculate the period of the sawtooth waveform generated in Example 7.7. What are the
voltages that correspond to the digital values 20, 30, 50, 127, and 192?
E7.9 Write a program to generate a sine waveform from the V OUT A pin in Figure 7.36.
E7.10 Write a program to generate a 1-kHz periodic square wave from the V OUT A pin and a
2-kHz periodic square wave from the V OUT B pin in Figure 7.36.
E7.11 Write a program to generate a periodic square wave from the V OUT A pin and let the
frequency switch between 1 and 4 kHz every 5 s in Figure 7.36.
E7.12 Write a program to generate the waveform shown in Figure 7E.13 from the pin V OUT A in
Figure 7.36.

4 V

2 V

1 ms 1 ms 1 ms 1 ms 1 ms

1 ms

Figure 7E.13 ■ A waveform to be generated