Hardware Reference
In-Depth Information
A demo board can be switched from one category to another. For example, a demo board
programmed with the D-Bug12 monitor can be reprogrammed with the serial monitor and allow
the user to employ CodeWarrior to develop software. If a demo board has the BDM interface
circuit (a 6-pin connector), then the user can also use a BDM adaptor and CodeWarrior (or other
IDE) to develop the software. If the user prefers to employ the D-Bug12 monitor, he or she can
use a BDM adaptor to program the D-Bug12 monitor into the microcontroller of the demo board
and start to use the D-Bug12 commands to debug the software.
It is obvious that different people will have different opinions on the choice of which HCS
demo board is best for learning the HCS12 microcontroller. Some educators prefer a demo board
to be a bare kit but allow the user to connect a wide variety of chips and I/O devices to the
demo board. Other educators may prefer a demo board to have a lot of features and also allow
the user to connect many other I/O devices and peripheral chips to the demo board. However,
all educators would agree that the demo board must be affordable. For the demo board to have
many features and still be affordable, in this text we use the Dragon12-Plus demo board from
Wytec to test and debug all the programs. The Dragon12-Plus and its predecessors have been
very popular in universities.
3.3 The Dragon12-Plus Demo Board
A photo of the Dragon12-Plus demo board is shown in Figure 3.1. In addition to the
9S12DG256B MCU, the Dragon12-Plus demo board has the following features:
Dual RS232 communication ports
DS1307 real-time clock (RTC) with backup battery included for testing I 2 C interface
CAN port
A 10-bit dual-channel DAC LTC1661
Four robot servo controllers with terminal block for external 5 V
Four 7-segment displays
Figure 3.1 Dragon12-Plus demo board
 
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