Page 161 - Programming Microcontrollers in C

146 Chapter 3 What Are Microcontrollers?

In some cases, a complete symbolic debug environment can be es­
tablished. P & E Microcomputer Systems, Inc., has a file system that
allows transfer of source code to the program. This source code is
displayed in the code window. It helps during the debug procedure to
see the source code while stepping through it. This capability is avail­
able with the compiler used for the MC68HC05, but not for the
MC68HC11 and MC68HC16 families.
All of the software written by P & E runs under the DOS operating
system. Today, there are fewer computers that run under DOS than
in the past, so you might want to find a later development system that
runs under a more modern operating system. I have always used DOS
by itself or running under either Windows 3.1 or one of the later
Windows operating systems. During the availability of OS/2, it was
an ideal operating system to develop microcontrollers under these
DOS-based development systems. More recent systems require
Windows 95 or later.
Development is enhanced if the host computer has multitasking
capability. This capability can come from any of the popular operat­
ing systems, such as Microsoft Windows or X Windows. In such a
case, it is possible to keep an editor with the listing file of the pro­
gram being debugged in a window along with the P & E display in
another window. This approach provides both insight into the code
being developed along with the condition of the hardware as the ex­
ecution of the code proceeds. It is recommended that this approach
be used when debugging programs on evaluation boards.
Unfortunately, none of these evaluation boards allows access to
the operation of the component being debugged when the device is
executing the test code. To achieve this level of operation would in­
crease the complexity of the development board significantly. Also
note there is no provision for a trace buffer on these boards. The
newer boards, EVS and MC68HC16EVB, provide headers that can
be connected to a logic analyzer that can act as a trace buffer and
provide many of the functions usually found in the more compre­
hensive development devices.
One last development device used is the MC68HC16EVB, shown
in Figure 3-5. This board differs from the others in one significant
way. The MC68HC16 family of devices (as well as those found in
the MC68300 family) provide a capability not usually found in most