Fujitsu MHW2080BS, MHW2100BS manual Status field, Bit 7 Busy BSY bit, Bit 6 Device Ready Drdy bit

5.2 Logical Interface

(8)Status field

The contents of this field indicate the status of the device. The contents of this field are updated at the completion of each command. When the BSY bit is 1, other bits of this field, are invalid.

Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit	2	Bit	1	Bit 0
BSY	DRDY	DF	DSC	DRQ	0		0		ERR

- Bit 7: Busy (BSY) bit.

This bit is set whenever the Command filed of the shadow block registers for the host system is accessed.

Then this bit is cleared when the command is completed. However, even if a command is being executed, this bit is cleared during the PIO data transfer request.

When BSY bit is 1, the host system should not write the shadow block registers. This bit is set by the device under following conditions:

(a)After COMRESET or SRST is set in the Device Control Field, the BSY bit is set, then the BSY bit is cleared, when the COMRESET process is completed.

The BSY bit is set for no longer than 15 seconds after the IDD accepts reset.

-Bit 6: Device Ready (DRDY) bit.

	This bit indicates that the device is capable to respond to a command.
	The IDD checks its status when it receives a command. If an error is detected (not
	ready state), the IDD clears this bit to 0. This is cleared to 0 at power-on and it is
	cleared until the rotational speed of the spindle motor reaches the steady speed.
- Bit 5:	Device Write Fault (DF) bit.
	This bit indicates that a device fault (write fault) condition has been detected.
	If a write fault is detected during command execution, this bit is latched and
	retained until the device accepts the next command or reset.
- Bit 4:	Device Seek Complete (DSC) bit.
	This bit indicates that the device heads are positioned over a track.
	In the IDD, this bit is always set to 1 after the spin-up control is completed.
- Bit 3:	Data Request (DRQ) bit.
	This bit indicates that the device is ready to transfer PIO data of word unit or byte
	unit between the host system and the device.
- Bit 2:	Always 0.
- Bit 1:	Always 0.
- Bit 0:	Error (ERR) bit.
	This bit indicates that an error was detected while the previous command was
	being executed. The Error field indicates the additional information of the cause
	for the error.

C141-E249 5-27