Texas Instruments 990 Operation Manual page 227

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APPENDIX B
STAND-ALONE PROGRAMMING
To run a stand-alone program on the 990, the user must provide initialization procedures for the
computer. Generally, these are the initialization of a workspace, the status register, and possibly
the interrupt vectors.
The simplest case, shown in figure B-1, can be used for a program that
will
run without
interrupts. Note that a power-up (level 0) interrupt may still occur and will not be handled. The
first two instructions set the initial status and workspace pointer. The END statement causes the
assembler to pass information to the loader about the starting location (STRT) of the program.
Figure B-2
is
an example which initializes some interrupt vectors. and supports five levels of
interrupts. A routine, provided for the real time clock, counts the number of seconds since
power-up. Note that if the routine is reused without reloading the program, the initialization
should include resetting the seconds and individual clock interval counters
in
the workspace for
the real time clock interrupt. Also note that the interrupt processor for memory errors resets the
interrupt by communicating through the CRU.
Bl
Digital Systems Division .