LPC47M14X datasheet(27/205 Pages) SMSC

27 / 205 page

SMSC DS – LPC47M14X

Page 27

Rev. 03/19/2001

6.5.1

FDC Internal Registers

The Floppy Disk Controller contains eight internal registers, which facilitate the interfacing between the host

microprocessor and the disk drive. Table 3 shows the addresses required to access these registers. Registers other

than the ones shown are not supported. The rest of the description assumes that the primary addresses have been

selected.

Table 3 – Status, Data and Control Registers

(Shown with base addresses of 3F0 and 370)

PRIMARY

ADDRESS

SECONDARY

ADDRESS

R/W

3F0

3F1

3F2

3F3

3F4

3F5

3F6

3F7

370

371

372

373

374

375

376

377

R/W

Status Register A (SRA)

Status Register B (SRB)

Digital Output Register (DOR)

Tape Drive Register (TSR)

Main Status Register (MSR)

Data Rate Select Register (DSR)

Data (FIFO)

Reserved

Digital Input Register (DIR)

Configuration Control Register (CCR)

STATUS REGISTER A (SRA)

Address 3F0 READ ONLY

This register is read-only and monitors the state of the internal interrupt signal and several disk interface pins in

PS/2 and Model 30 modes. The SRA can be accessed at any time when in PS/2 mode. In the PC/AT mode the data

bus pins D0 - D7 are held in a high impedance state for a read of address 3F0.

PS/2 Mode

INT

PENDIN

nDRV2

STEP

nTRK0

HDSEL

nINDX

nWP

DIR

RESET

COND.

N/A

BIT 0 DIRECTION

Active high status indicating the direction of head movement. A logic "1" indicates inward direction; a logic "0"

indicates outward direction.

BIT 1 nWRITE PROTECT

Active low status of the WRITE PROTECT disk interface input. A logic "0" indicates that the disk is write protected.

BIT 2 nINDEX

Active low status of the INDEX disk interface input.

BIT 3 HEAD SELECT

Active high status of the HDSEL disk interface input. A logic "1" selects side 1 and a logic "0" selects side 0.

BIT 4 nTRACK 0

Active low status of the TRK0 disk interface input.

BIT 5 STEP

Active high status of the STEP output disk interface output pin.

BIT 6 nDRV2

This function is not supported. This bit is always read as “1”.

BIT 7 INTERRUPT PENDING

Active high bit indicating the state of the Floppy Disk Interrupt output.

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