LPC47M14X datasheet(39/205 Pages) SMSC

39 / 205 page

SMSC DS – LPC47M14X

Page 39

Rev. 03/19/2001

Table 16 – Status Register 3

BIT NO.

SYMBOL

NAME

DESCRIPTION

Unused. This bit is always "0".

Write

Protected

Indicates the status of the WP pin.

Unused. This bit is always "1".

Track 0

Indicates the status of the TRK0 pin.

Unused. This bit is always "1".

Head Address Indicates the status of the HDSEL pin.

1,0

DS1,0

Drive Select

Indicates the status of the DS1, DS0 pins.

RESET

There are three sources of system reset on the FDC: the PCI_RESET# pin, a reset generated via a bit in the DOR, and

a reset generated via a bit in the DSR. At power on, a Power On Reset initializes the FDC. All resets take the FDC out

of the power down state.

All operations are terminated upon a PCI_RESET#, and the FDC enters an idle state. A reset while a disk write is in

progress will corrupt the data and CRC.

On exiting the reset state, various internal registers are cleared, including the Configure command information, and the

FDC waits for a new command. Drive polling will start unless disabled by a new Configure command.

PCI_RESET# Pin (Hardware Reset)

The PCI_RESET# pin is a global reset and clears all registers except those programmed by the Specify command. The

DOR reset bit is enabled and must be cleared by the host to exit the reset state.

DOR Reset vs. DSR Reset (Software Reset)

These two resets are functionally the same. Both will reset the FDC core, which affects drive status information and the

FIFO circuits. The DSR reset clears itself automatically while the DOR reset requires the host to manually clear it. DOR

reset has precedence over the DSR reset. The DOR reset is set automatically upon a pin reset. The user must

manually clear this reset bit in the DOR to exit the reset state.

MODES OF OPERATION

The FDC has three modes of operation, PC/AT mode, PS/2 mode and Model 30 mode. These are determined by the

state of the Interface Mode bits in LD0-CRF0[3,2].

PC/AT mode

The PC/AT register set is enabled, the DMA enable bit of the DOR becomes valid (controls the interrupt and DMA

functions), and DENSEL is an active high signal.

PS/2 mode

This mode supports the PS/2 models 50/60/80 configuration and register set. The DMA bit of the DOR becomes a

"don't care". The DMA and interrupt functions are always enabled, and DENSEL is active low.

Model 30 mode

This mode supports PS/2 Model 30 configuration and register set. The DMA enable bit of the DOR becomes valid

(controls the interrupt and DMA functions), and DENSEL is active low.

DMA TRANSFERS

DMA transfers are enabled with the Specify command and are initiated by the FDC by activating a DMA request cycle.

DMA read, write and verify cycles are supported. The FDC supports two DMA transfer modes: Single Transfer and

Burst Transfer. Burst mode is enabled via Logical Device 0-CRF0-Bit[1] (LD0-CRF0[1]).

CONTROLLER PHASES

For simplicity, command handling in the FDC can be divided into three phases: Command, Execution, and Result. Each

phase is described in the following sections.

Command Phase

After a reset, the FDC enters the command phase and is ready to accept a command from the host. For each of the

commands, a defined set of command code bytes and parameter bytes has to be written to the FDC before the

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