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SYSLIB Access Methods
This type of switching between relocatable and common bank versions of a routine can
be done as long as the calling program makes use of the I$BJ instruction instead of an
LMJ or LIJ instruction to call the SYSLIB routines. For SYSLIB routines with a calling
procedure, the field that determines the type of call to make to the routine must be set
to 'CB' (common bank). If the field is set to 'A' (call the common bank version of the
routine using the Auto Switch calling sequence) or left blank (a blank field means call the
relocatable version of the routine), then the calling procedure generates an LMJ
instruction. If an LMJ instruction or an LIJ instruction is generated to call the routine,
then the program cannot switch between the common bank version and the relocatable
version as described above.
The I$BJ instruction is necessary because it remains undefined until the program is
collected. At collection time, the I$BJ is resolved to an LMJ if the label being referenced
resides in the same bank as the instruction referencing it, or it is resolved to an LIJ if the
label is in another bank. Programs written before the implementation of the I$BJ routine
may contain calling sequences such as the one that follows.
LXI,U X11,PIRCB$
LIJ X11,BASCFD$
This sequence requires the calling program to know which common bank contains the
routine as well as the name of the routine. Since the LIJ instruction is explicitly coded
into this program, it always calls the common bank version of the SYSLIB ASCII to
Fieldata routine. The program would have to be rewritten and reassembled to make it
reference the relocatable version of the SYSLIB routine. A more flexible calling
sequence is
I$BJ X11,CBFDASC$
The I$BJ procedure determines whether or not to generate a call to a common bank
based on the label included on the call, in this case. If a common bank call is generated,
the procedure handles retrieving the bank descriptor index of the common bank. Prior to
executing the above calling sequence, the calling program must ensure that the correct
values required by the SYSLIB routine have been loaded into the correct registers.
For more information on common bank calls and the I$BJ routine, consult the Collector
Programming Reference Manual.
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