Fujitsu MHW2040AC User Manual download pdf (Page 88)

Interface

- Bit 7: Busy (BSY) bit. This bit is set whenever the Command register is

accessed. Then this bit is cleared when the command is completed.

However, even if a command is being executed, this bit is 0 while data

transfer is being requested (DRQ bit = 1). When BSY bit is 1, the host

system should not write the command block registers. If the host

system reads any command block register when BSY bit is 1, the

contents of the Status register are posted. This bit is set by the device

under following conditions:

(a) Within 400 ns after RESET- is negated or SRST is set in the

Device Control register, the BSY bit is set. The BSY bit is

cleared, when the reset process is completed.

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

accepts reset.

(b) Within 400 ns from the host system starts writing to the Command

of the READ SECTOR(S), WRITE SECTOR(S), or WRITE

BUFFER command.

- 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: The 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 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 register indicates

the additional information of the cause for the error.

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Fujitsu MHW2040AC User Manual Page 88