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Chapter 4: Software
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Chapter 4:
Software
Please refer to the Technical Manual of the “C/C++ Development Kit for TERN 16-bit Embedded
Microcontrollers” for details on debugging and programming tools.
For details regarding software function prototypes and sample files demonstrating their use, please refer to
the Software Glossary in Appendix F.
Guidelines, awareness, and problems in an interrupt driven environment
Although the C/C++ Development Kit provides a simple, low cost solution to application engineers, some
guidelines must be followed. If they are not followed, you may experience system crashes, PC hang-ups,
and other problems.
The debugging of interrupt handlers with the Remote Debugger can be a challenge. It is possible to debug
an interrupt handler, but there is a risk of experiencing problems. Most problems occur in multi-interrupt-
driven situations. Because the remote kernel running on the controller is interrupt-driven, it demands
interrupt services from the CPU. If an application program enables interrupt and occupies the interrupt
controller for longer than the remote debugger can accept, the debugger will time-out. As a result, your PC
may hang-up. In extreme cases, a power reset may be required to restart your PC.
For your reference, be aware that our system is remote kernel interrupt-driven for debugging.
The run-time environment on TERN controllers consists of an I/O address space and a memory address
space. I/O address space ranges from 0x0000 to 0xffff, or 64 KB. Memory address space ranges from
0x00000 to 0xfffff in real-mode, or 1 MB. These are accessed differently, and not all addresses can be
translated and handled correctly by hardware. I/O and memory mappings are done in software to define
how translations are implemented by the hardware. Implicit accesses to I/O and memory address space
occur throughout your program from TERN libraries as well as simple memory accesses to either code or
global and stack data. You can, however, explicitly access any address in I/O or memory space, and you
will probably need to do so in order to access processor registers and on-board peripheral components
(which often reside in I/O space) or non-mapped memory.
This is done with four different sets of similar functions, described below.
poke/pokeb
Arguments: unsigned int segment, unsigned int offset, unsigned int/unsigned char data
Return value: none
These standard C functions are used to place specified data at any memory space location. The segment
argument is left shifted by four and added to the offset argument to indicate the 20-bit address within
memory space. poke is used for writing 16 bits at a time, and pokeb is used for writing 8 bits.
The process of placing data into memory space means that the appropriate address and data are placed on
the address and data-bus, and any memory-space mappings in place for this particular range of memory will
be used to activate appropriate chip-select lines and the corresponding hardware component responsible for
handling this data.
