PC87306 datasheet(14/110 Pages) NSC

14 / 110 page

10 Pin Description (Continued)

TABLE 1-1 Pin Descriptions (Alphabetical)

(Continued)

Symbol

Function

SIN1 2

110 102

Serial Input

This input receives composite serial data from the communications link (eg peripheral

device MODEM or data set)

SLCT

124

Select

When a printer is connected it sets this input high This pin has a nominal 25 kX pull-down

resistor attached to it

SLIN

123

Select Input

When this signal is low it selects the printer This pin is a TRI-STATE condition 10 ns

aftera0is loaded into the corresponding Control Register bit The system should pull this pin high

using a 47 kX resistor

SOUT1 2

108 98

Serial Output

This output sends composite serial data to the communications link (peripheral

device MODEM or data set) The SOUT signal is set to a marking state (logic 1) after a Master

Reset operation (See BOUT and BADDR1 for further information)

STB

137

Data Strobe

This output indicates to the printer that valid data is available at the printer port This

pin is in a TRI-STATE condition 10 ns after a zero is loaded into the corresponding Control Register

bit The system should pull this pin high using a 47 kX resistor (See WRITE for further information)

STEP

Step

This output signal issues pulses to the disk drive at a software programmable rate to move

the head during a seek operation

SYSCLK

System Clock

This input is used as the KBC input clock when bit 7 of KRR is 1

Terminal Count

Control signal from the DMA controller to indicate the termination of a DMA

transfer TC is accepted only when FDACK or PDACK is active TC is active high in PC-AT mode

and active low in PS2 mode

TRK0

Track 0

This input indicates to the controller that the head of the selected floppy disk drive is at

track zero

VBAT

Battery

Real-Time Clock battery pin

VDD

160 140

Digital Supply

This is the 5V supply voltage for the digital circuitry

99 57

41 17

VSS

159 149

Digital Ground

This is the ground for the digital circuitry

139 132

121 100

90 80

58 40

32 10

WAIT

126

Wait

This signal is used in EPP mode by the parallel port device to extend its access cycle It is

active low (See BUSY and Table 8-5 for further information)

Write

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

WDATA

Write Data

This output is the write precompensated serial data that is written to the selected floppy

disk drive Precompensation is software selectable

WGATE

Write Gate

This output signal enables the write circuitry of the selected disk drive WGATE has

been designed to prevent glitches during power up and power-down This prevents writing to the

disk when power is cycled

Write Protect

This input indicates that the floppy disk in the selected drive is write protected

WRITE

137

Write Strobe

This signal is used in EPP mode as a write strobe It is active low (See STB and

Table 8-5 for further information)

Clock Oscillator

A TTL or CMOS compatible 24 MHz clock is connected to this pin

X1C

Crystal1 Slow

Input for the internal Real-Time Clock crystal oscillator amplifier

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