To build the UITs, HCD or IPL calls all UIMs at initialization time. For each device type or model supported by the UIM the UIM must build unit information parameters (UIP) and call the build UIT routine.

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

UIT Build Routine Input Parameters

A UIM provides the input to the UIT build routine in the unit information parameters (UIP). The UIP resides in the UIM and is mapped by CBDZUIP.

Registers on Entry to the UIT 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 UIP

Register 2-12

Undefined

Register 13

Address of an 18-word save area

Register 14

Return address

Register 15

The UIT build routine entry point address

Registers on Exit from the UIT Build Routine

Register 0-14

Restored

Register 15

Return code

Return Codes

RC 0

No errors detected, UIT built

RC 8

Error detected, no UIT built, message written