To build switch information tables (SIT), HCD and IPL call all UIMs at initialization time. A UIM that defines switches must call the SIT build routine once for each type of ESCON director that it defines. A separate SIT is built for each ESCON director type.

A UIM invokes the SIT build routine, in 31-bit addressing mode, by using a BALR instruction. Use the standard register save area conventions. The address of the SIT build routine is in the field UCASITP in the UCA.

SIT Build Routine Input Parameters

A UIM provides the input to the SIT build routine in the switch information parameters (SIP). The SIP resides in the UIM and is mapped by CBDZSIP.

Registers on Entry to the SIT Build Routine

Register 0

Undefined

Register 1

Pointer to a two-word parameter list

• Word 1 - Address of the UCA
• Word 2 - Address of the SIP

Register 2-12

Undefined

Register 13

Address of an 18-word save area

Register 14

Return address

Register 15

The SIT build routine entry point address

Registers on Exit from the SIT Build Routine

Register 0-14

Restored

Register 15

Return code

Return Codes

RC 0

No errors detected, SIT built

RC 8

Error detected, no SIT built, message written