PC87310 datasheet(11/52 Pages) NSC

11 / 52 page

20 Pin Descriptions (Continued)

Pin Symbol

Pin Number

Description

SLCT

(Select)

This input is set high by the printer when it is selected

SLIN

(Select Input)

This output selects the printer when it is low This pin will be in a

TRI-STATE condition 10 ns after a zero is loaded into the corresponding

Control Register bit position The system should pull this pin high using a

47 kX resistor

SOUT1 2

57 41

This output sends composite serial data output to the communications

(Serial Output)

link (peripheral MODEM or data set) The SOUT signal is set to the

Marking (logic 1) state upon a Master Reset operation (See BOUT1 2

and CRB0 7 for further information on these pins)

STB

(Data Strobe)

This output indicates to the peripheral that the data at the parallel port is

valid This pin will be in a TRI-STATE condition 10 ns after a zero is

loaded into the corresponding Control Register bit position The system

should pull this pin high using a 47 kX resistor

STEP

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

(Terminal Count)

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

signal is enabled when the DMA Acknowledge pin is active

TRK0

(Track 0)

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

zero of the selected disk drive

VDD A B C D (Power)

81 74 45 34

5V Supply to the FDC analog FDC digital serial ports and parallel

port circuitry respectively

VSS A B C D E F

77 100 65

0V Reference for the FDC analog FDC digital CPU interface serial

(Ground)

59 27 89

ports parallel port and disk interface output drive circuitry respectively

WDATA

(Write Data)

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

(Write Gate)

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

WPROT

(Write Protect)

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

(Write)

When this input is low while the chip is selected the CPU can write

control words or data into the selected register

XTSEL

(XT Select)

When this input is low during reset the chip will operate in the XT

compatible mode When this input is high during reset this chip will

operate in the AT compatible mode This pin must always have a pull

down or pull up resistor attached to it (See GPEN and GRD for further

information on this pin)

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