7526 DCT Reference
All 7526 ROM microcode Application Program Interfaces (APIs)
use a PC-DOS style interface. That is, parameters are
placed in processor registers and the appropriate software interrupt
is invoked. Thus, it is possible to use the APIs from any language that
can both write to and read from the processor registers, either directly
or indirectly.
To facilitate use of the APIs from high level languages,
an API library is supplied which supports the C language calling
convention.
The library modules are coded in assembly language. Each
module takes passed parameters from the stack and places them in the
appropriate processor registers, invokes the software interrupt and
writes any returned values from the processor registers into variables
indicated by passed pointers.
Because the current language compilers support mixed memory models,
the 7526 API library uses a large model interface. For applications
written in C/2, it is essential to include the subsystem header file,
CFRAPI26.H for the APIs used in the program.
The CFRAPI26.H file contains function
prototypes for each API in the subsystem.
These prototypes will cause
the compiler to generate the correct calling sequence regardless of the
memory model used by the application.
The header file also contains
definitions of manifest constants and structures used with the APIs.
The defined constants should be used exclusively to avoid conflicts
with possible future changes to an API.