Maxtor 6800 Control Diagnostic Registers, Alternate Status Register, Device Control Register

HOST SOFTWARE INTERFACE

Control Diagnostic Registers

These I/O port addresses reference three Control/Diagnostic registers:

I/O PORT	READ	WRITE
3F6h	Alternate Status	Fixed Disk Control
3F7h	Digital Input	Not used

Alternate Status Register

Contains the same information as the Status register in the Task File. However, this register may be read at any time without clearing a pending interrupt.

Device Control Register

Contains the software Reset and Enable bit to enable interrupt requests to the host. Bit definitions follow:

7	6	5	4	3	2	1	0
0	0	0	0	0	SRST	IEN	0
					Reset	IRQ Enable

Reset – Setting the software Reset bit holds the drive in the reset state. Clearing the bit re-enables the drive. The software Reset bit must be held active for a minimum of 5 µsec.

IRQ Enable – Setting the Interrupt Request Enable to 0 enables the IRQ 14 signal to the host. When this bit is set

to 1, IRQ14 is tri-stated, and interrupts to the host are disabled. Any pending interrupt occurs when the bit is set to 0. The default state of this bit after power up is 0 (interrupt enabled).

Digital Input Register

Contains information about the state of the drive. Bit definitions follow:

7	6	5	4	3	2	1	0
x	-WG	-HS3	-HS2	-HS1	-HS0	-DS1	DS0
Reserved		Head	Head	Head	Head	Drive	Drive
	Gate	Select 3	Select 2	Select 1	Select 0	Select 1	Select 0

Bit 7 of the host data bus is not driven when this register is read.

-Write Gate – Reflects the state of the active low write gate signal on the drive.

-Head Select 3 through -Head Select 0 – Represents the ones complement of the currently selected head number.

-Drive Select 1 – Is 0 if drive 1 selected; 1 otherwise.

-Drive Select 0 – Is 0 if drive 0 selected; 1 otherwise.

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