PC97338VLJ datasheet(69/221 Pages) NSC

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3.0 The Digital Floppy Disk

Controller (FDC)

The Floppy Disk Controller (FDC) is suitable for all

PC-AT, EISA, PS/2, and general purpose applica-

tions. DP8473 and N82077 software compatibility is

provided. Key features include a 16-byte FIFO, PS/2

diagnostic register support, perpendicular recording

mode, CMOS disk input and output logic, and a high

performance Digital Data Separator (DDS).

Figure 41shows a functional block diagram of the

FDC. The rest of this Section describes the FDC func-

tions, data transfer, the FDC registers, the phases of

FDC commands, the result phase status registers and

the FDC commands, in that order.

3.1

FDC FUNCTIONS

The Chip is software compatible with the DP8473 and

82077 Floppy Disk Controllers (FDCs). Upon a pow-

er-on reset, the 16-byte FIFO is disabled. Also, the

disk interface output signals are configured as active

push-pull output signals, which are compatible with

both CMOS input signals and open-collector resistor

terminated disk drive input signals. The FIFO can be

enabled with the CONFIGURE command. The FIFO

can be very useful at high data rates, with systems

that have a long DMA bus latency, or with multi-task-

ing systems such as the EISA or MCA bus structures.

The FDC supports all the DP8473 MODE command

features as well as some additional features. These

include control over the enabling of the FIFO for read

and write operations, disabling burst mode for the

FIFO, a bit that will configure the disk interface out-

puts as open-drain output signals, and programmabil-

ity of the DENSEL output signal.

3.1.1

Microprocessor Interface

The FDC interface to the microprocessor consists of

the A9-3, AEN, RD, and WR signals, which access

the chip for read and write operations; the data sig-

nals D7-0; the address lines A2-0, which select the

appropriate register (see Table 35); the IRQ6 signal,

and the DMA interface signals DRQ, DACK, and TC.

It is through this microprocessor interface that the

Floppy Disk Controller (FDC) receives commands,

transfers data, and returns status information.

FIGURE 41. FDC Functional Block Diagram

Internal Control and Data Bus

Interface

Logic

Address

Decoder

DMA

Enable

Logic

Main Status

16-Byte

FIFO

(MSR)

PC8477B

Micro-Engine

and

Timing/Control

Logic

Data Rate

Selection

(DSR)

Configuration

Control

(CCR)

2 KB x 16

Micro-Code

Status

Digital Input

(DIR)

Digital Output

(DOR)

Write

Precompen-

Digital

Data

Separator

(DDS)

Disk

Input

and

Output

Logic

DRATE1,0

DENSEL

DIR

DR1

DR23

HDSEL

MTR0

sator

MTR1

STEP

WGATE

WDATA

DSKCHG

DRV2

INDEX

RDATA

TRK0

MSEN1,0

FDC Chip

A2-0

Reset

D7-0

FDC DMA

Interrupt

FDC Clock

Select

Acknowledge

Request

DR0

PC97338VLJ Datasheet(PDF) 69 Page - National Semiconductor (TI)

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