BASIC PROGRAMMING
SECTION 4.8
4.8.8
4.8.9
4.8.10
4. 8. 11
4.8.12
VER.V09F
It should be remembered that these locations are allocated
dynamically and are entirely dependent upon the program and
store. Also, if CLEAR or a new program line is inserted then
the data storage is removed, so DEFLIM will point to the top of
memory and ALIM to the top of the program. Hence, the program
should be RUN before using these values. Clearly, if Basic is
only used to start a large machine code program then there will
be no variables and only a small amount of Basic source.
SYSTEM CALLS
The system calls are all defined in section 3.5, CP/M INTERFACE.
They should be used by CALLing location 5 with the relevant
value in C for CP/M compatibility. NO guarantee is made of the
contents of undefined registers on exit and in general all
register contents will be destroyed.
TIIE
STACK
The machine code stack pointer is initialised at switch on. It
is not recommended that it should be moved as the system can use
a considerable amount of stack space. Under no circumstances
should routines be written which preclude the use of interrupts;
V24 I/0 uses them liberally.
ON/OFF
The key, as detailed in section 2.4.13, ON/OFF KEY, is software
controlled. The keyboard should be scanned periodically in any
user written software if manual power OFF is required.
TIIE NSC800
It is not proposed to go into software techniques, meaning of
object code, etc., here as the NSC800 is totally software
compatible to the 280. A list of the machine code instructions
is presented in section 9.4, NSC800 MACHINE CODE. Users are
referred to any tutorial book on the 280 for detailed
programming information.
EXECUTION TIME
Of interest in machine code loops, etc., is the execution time
of the program. The number of cycles used by each instruction
is detailed in section 9.4, NSC800 MACHINE CODE. The cycle time
in HUNTER is 250ns.
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