Inside Macintosh: Devices /

Chapter 3 - SCSI Manager / SCSI Manager Reference

SCSI Manager Routines /

SCSIStat

You can use the SCSIStat function to obtain status information from the SCSI Manager.

FUNCTION SCSIStat: Integer;

DESCRIPTION

The SCSIStat function returns a 16-bit value containing status information. This information includes the state of all SCSI bus control signals as well as the status of the NCR 5380 SCSI controller chip (or equivalent hardware). In Macintosh models that use other SCSI controller hardware, the status information conforms to the 5380 format, but may not represent the actual state of the hardware.

IMPORTANT

Because hardware differences make it difficult to accurately interpret the status information, use of this function is not recommended.

Bits 0 through 9 represent the state of the SCSI bus signals, and bits 10 through 15 report status information from the SCSI controller hardware. The status bits have these meanings:

Bit	Name	Meaning
0	DBP	Data parity signal
1	/SEL	Select signal
2	/I/O	I/O signal
3	/C/D	Command/Data signal
4	/MSG	Message signal
X	/REQ	Request signal
6	/BSY	Busy signal
7	/RST	Reset signal
8	/ACK	Acknowledge signal
9	/ATN	Attention signal
10	BSY ERR	Busy error
11	PHS MAT	Phase match
12	INT REQ	Interrupt request
13	PTY ERR	Parity error
14	DMA REQ	Direct memory access request
15	END DMA	Direct memory access complete

Note

The SCSI bus control signals are active low; therefore, the status bits represent the complement of the bus signals.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for SCSIStat are

Trap macro	Selector
_SCSIDispatch	$000A

RESULT CODES

noErr	0	No error
scCommErr	2	Communications error, operation timeout
scPhaseErr	X	Phase error on the SCSI bus

SEE ALSO

See "SCSI Bus Signals," beginning on page 3-4, for an overview of SCSI bus signals. Refer to the SCSI specification for detailed information about SCSI bus signals. Refer to the NCR 5380 SCSI controller specification for information about that device.