Symbol

DP8473

DP8473

Function

PCC

DIP

MTR0

8

6

This is an active low motor enable line for drive 0 which is controlled by the Drive Control

register This is a high drive open drain output

MTR1

7

5

This is an active low motor enable line for drive 1 Similar to MTR0

MTR2

1

This is an active low motor enable line for drive 2 Similar to MTR0

MTR3

52

This is an active low motor enable line for drive 3 Similar to MTR0

OSC1

38

36

One side of an external 24 MHz crystal is attached here This pin is tied low if an external

clock is used

OSC2CLOCK

37

35

One side of the external 24 MHz crystal is attached here If a crystal is not used a TTL or

CMOS compatible clock is connected to this pin

PUMPPREN

46

42

When the PU bit is set in Mode Command this pin is an output that indicates when the

charge pump is making a correction Otherwise this pin is an input that sets the precomp

mode as shown in Table VI If pin is configured as PUMP PREN is assumed high

RD

17

15

Active low input to signal a read from the controller to the microprocessor

RDATA

44

41

The active low raw data read from the disk is connected here This is a Schmitt input

RESET

15

13

Active high input that resets the controller to the idle state and resets all the output lines

to the disk drive to their disabled state The Drive Control register is reset to 00 The Data

Rate register is set to 250 kbs The Specify command registers are not affected The

Mode Command registers are set to the default values Reset should be held active

during power up To prevent glitches activating the reset sequence a small capacitor

(1000 pF) should be attached to this pin

RPMLC

51

47

This high drive open drain output pin has two functions based on the selection of the

DRVTYP pin

1 When using a dual speed spindle motor floppy drive (DRVTYP pin low) this output is

used to select the spindle motor speed either 300 RPM or 360 RPM In this mode this

output goes low when 250300 kbdata rate is chosen in the data rate register and high

when 500 kbs is chosen

2 When using a single speed spindle motor floppy drive (DRVTYP pin high) this pin

indicates when to reduce the write current to the drive This output is high for high density

media (when 500 kbs is chosen)

SETCUR

48

44

An external resistor connected from this pin to analog ground programs the amount of

charge pump current that drives the external filters The PLL Filter Design section shows

how to determine the values

STEP

50

46

This active low open drain high drive output will produce a pulse at a software

programmable rate to move the head during a seek operation

TC

33

31

Active high input to indicate the termination of a DMA transfer This signal is enabled

when the DMA Acknowledge pin is active

TRK0

10

8

This active low Schmitt input tells the controller that the head is at track zero of the

selected disk drive

WDATA

3

1

This is the active low open drain write precompensated serial data to be written onto the

selected disk drive This is a high drive open drain output

WGATE

49

45

This active low open drain high drive output enables the write circuitry of the selected

disk drive This output has been designed to prevent glitches during power up and power

down This prevents writing to the disk when power is cycled

WR

16

14

Active low input to signal a write from the microprocessor to the controller

WRT PRT

12

10

This active low Schmitt input indicates that the disk is write protected Any command that

writes to that disk drive is inhibited when a disk is write protected

14

12

This pin is the 5V supply for the digital circuitry

13

11

This pin is the 5V supply for the analog data separator circuitry

4