Fujitsu MHV2120AT User Manual download pdf (Page 90)

Interface

5-14 C141-E218

(2) Device Control register (X’3F6’)

The Device Control register contains device interrupt and software reset.

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

HOB X X X X SRST nIEN 0

- Bit 7:

High Order Byte (HOB) is the selector bit that selects higher-order

information or lower-order information of the EXT system command.

If HOB = 1, LBA bits 47 to 24 and the higher-order 8 bits of the sector

count are displayed in the task register.

If HOB = 0, LBA bits 23 to 0 and the lower-order 8 bits of the sector

count are displayed in the task register.

- Bit 2:

Software Reset (SRST) is the host software reset bit. When this bit is

set, the device is held reset state. When two devices are daisy chained

on the interface, setting this bit resets both devices simultaneously.

The slave device is not required to execute the DASP- handshake.

- Bit 1:

nIEN bit enables an interrupt (INTRQ signal) from the device to the

host. When this bit is 0 and the device is selected, an interruption

(INTRQ signal) can be enabled through a tri-state buffer. When this

bit is 1 or the device is not selected, the INTRQ signal is in the high-

impedance state.

5.3 Host Commands

The host system issues a command to the device by writing necessary parameters

in related registers in the command block and writing a command code in the

Command register.

The device can accept the command when the BSY bit is 0 (the device is not in

the busy status).

The host system can halt the uncompleted command execution only at execution

of hardware or software reset.

When the BSY bit is 1 or the DRQ bit is 1 (the device is requesting the data

transfer) and the host system writes to the command register, the correct device

operation is not guaranteed.

5.3.1 Command code and parameters

Table 5.3 lists the supported commands, command code and the registers that

needed parameters are written.

1 2 ... 85 86 87 88 89 90 91 92 93 94 95 ... 279 280

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Fujitsu MHV2120AT User Manual Page 90