Legacy Document

Inside Macintosh: Devices /

Chapter 2 - Slot Manager / Slot Manager Reference

Low-Level Routines /

SCalcStep

This function is used only by the Macintosh Operating System.

FUNCTION SCalcStep (spBlkPtr: SpBlockPtr): OSErr;

spBlkPtr

A pointer to a Slot Manager parameter block.

<--	spResult	LongInt	The function result.
-->	spsPointer	Ptr	A pointer to a byte in declaration ROM.
-->	spByteLanes	SignedByte	The byte lanes used.
-->	spFlags	SignedByte	Flags.

DESCRIPTION

The SCalcStep function calculates the field sizes in the block pointed to by spBlkPtr. It is used for stepping through the card firmware one field at a time. If the fConsecBytes flag is set the function calculates the step value for consecutive bytes; otherwise it calculates it for consecutive IDs.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the SCalcStep function are

Trap macro	Selector
_SlotManager	$0028

On entry, register D0 contains the routine selector and register A0 contains the address of the Slot Manager parameter block. When _SlotManager returns, register D0 contains the result code.

Registers on entry
A0	Address of the parameter block
D0	$0028

Registers on exit
D0	Result code

RESULT CODES

noErr	0	No error
smNoMoresRsrcs	-344	Requested sResource not found