CSI Invocation

CSI can be invoked in either 24-bit or 31-bit addressing mode. CSI is reentrant and reusable. CSI can be invoked in any protection key and in either supervisor or problem state.The module name of the CSI program is IGGCSI00; it is stored in SYS1.LINKLIB.

The invocation can be done by any of the following methods:

An assembler language CALL statement that results in a V-type address constant
An assembler language LINK macro
Assembler language LOAD and CALL macros
A high-level language that results in one of these types of invocation.

When CSI is invoked:

general-purpose register (GPR) 1 points to a parameter list
GPR 13 points to a standard register save area of length 72 bytes
GPR 14 contains the return address in the caller's program
GPR 15 contains the entry point of CSI.

The parameter list pointed to by GPR 1 has three fullword entries:

The first word of the parameter list contains a pointer to a 4-byte reason area used to return error or status information.
The second word points to a list of selection criteria fields used to communicate with CSI.
The third word points to a work area that contains data on return from CSI.

On return, a return code is passed in GPR 15 to indicate whether an error has occurred and the nature of the error. The first address in the parameter list points to a 4-byte reason area that contains information concerning the return code.