To build the CITs, HCD or IPL calls the UIMs for initialization. For each control unit type that a UIM defines, it must build control unit information parameters (CIP) and call the CIT BUILD Routine. A separate CIT is built for each control unit type.

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

CIT Build Routine Input Parameters

A UIM provides the input to the CIT build routine in the control unit information parameters (CIP). The CIP resides in the UIM and is mapped by CBDZCIP.

Registers on Entry to the CIT 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 CIP

Register 2-12

Undefined

Register 13

Address of an 18-word save area

Register 14

Return address

Register 15

The CIT build routine entry point address

Registers on Exit from the CIT Build Routine

Register 0-14

Restored

Register 15

Return code

Return Codes

RC 0

No errors detected, CIT built

RC 8

Errors detected, no CIT built, message written