Function Name: SETLFS

Purpose: Set channel LA, FA, SA
Call address: $FFBA (hex) 65466 (decimal)

	Registers:	.A = LA (logical #)
			.X = FA (device #)
			.Y = SA (secondary adr)
	Memory:		system map
	Flags:		none
	Calls:		none
	Registers:	none
	Memory:		LA, FA, SA updated
	Flags:		none

Description: SETLFS sets the logical file number (LA, $B8), device number (FA, $BA) and secondary address (SA, $B9) for the higher-level Kernal I/O routines. The LA must be unique among OPENed files and is used to identify specific files for I/O operations. The device number rangs is 0 to 31 and is used to target I/O. The SA is a command to be sent to the indicated device, usually to place it in a particular mode. If the SA is not needed, the .Y register should pass $FF. SETLFS is often used along with SETNAM and SETBNK calls prior to OPENs. See the Kernal OPEN, LOAD and SAVE calls for examples.