PC87311AVF datasheet(7/78 Pages) NSC

7 / 78 page

10 Pin Description (Continued)

Symbol

Function

A9–A0

21–30

Address

These address lines from the microprocessor determine which internal register is accessed

A0 – A9 are don’t cares during an FDC DMA transfer

ACK

Acknowledge

This input is pulsed low by the printer to indicate that it has received data from the

parallel port This pin has a nominal 25 kX pull-up resistor attached

AFD

Automatic Feed XT

When this signal is low the printer should automatically line feed after each line is

printed This pin will be 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

AEN

Address Enable

This input disables function selection via A9 – A0 when it is high Access to the FDC

Data Register during DMA transfer is NOT affected by this pin

BADDR0

Base Address

This bit determines one of two base addresses from which the Index and Data

Registers will be offset (see Table 2-2) An internal pull-down resistor of 40 kX is on each pin Use a

10 kX resistor to pull this pin to the required level during reset

BOUT12

73 65

BAUD Output

This multi-function pin provides the associated serial channel Baud Rate generator

output signal if test mode is selected in the Power and Test Configuration Register and the DLAB bit

(LCR7) is set After Master Reset this pin provides the SOUT function (See SOUT and CFG0 – 4 for

further information)

BUSY

Busy

This pin is set high by the printer when it can’t accept another character This pin has a nominal

25 kX pull-down resistor attached to it

CFG0 – 4

65 66

Default Configuration

These CMOS inputs select 1 of 32 default configurations in which the

PC87311A12 will power-up (see Table 2-1) An internal pull-down resistor of 40 kX is on each pin

71 73

Usea10kX resistor to pull these pins to the required level during reset

CSOUT

Chip Select Output

When the associated bit in the Power and Test Configuration Register is set this

multi-function pin provides an active signal each time the internal address decoder decodes an

address enabled for the PC87311A12 (See PWDN for further information)

CTS12

72 64

Clear to Send

When low this indicates that the MODEM or data set is ready to exchange data The

CTS signal is a MODEM status input whose condition the CPU can test by reading bit 4 (CTS) of the

MODEM Status Register (MSR) for the appropriate serial channel Bit 4 is the complement of the CTS

signal Bit 0 (DCTS) of the MSR indicates whether the CTS input has changed state since the previous

reading of the MSR CTS has no effect on the transmitter

Note

Whenever the DCTS bit of the MSR is set an interrupt is generated if MODEM Status interrupts are enabled

D7–D0

10–17

I O

Data

Bi-directional data lines to the microprocessor D0 is the LSB and D7 is the MSB These signals

all have 24 mA (sink) buffered outputs

DACK

DMA Acknowledge

Active low input to acknowledge the FDC DMA request and enable the RD and

WR inputs during a DMA transfer When in PC-AT or Model 30 mode this signal is enabled by bit D3 of

the Digital Output Register (DOR) When in PS2 mode DACK is always enabled and bit D3 of the

DOR is reserved DACK should be held high during PIO accesses

DCD12

77 69

Data Carrier Detect

When low this indicates that the data carrier has been detected by the MODEM

or data set The DCD signal is a MODEM status input whose condition the CPU can test by reading bit

7 (DCD) of the MODEM Status Register (MSR) for the appropriate serial channel Bit 7 is the

complement of the DCD signal Bit 3 (DDCD) of the MSR indicates whether the DCD input has

changed state since the previous reading of the MSR

Note

Whenever the DDCD bit of the MSR is set an interrupt is generated if MODEM Status interrupts are enabled

DENSEL

Density Select

Indicates when a high FDC density data rate (500 kbs or 1 Mbs) or a low density

data rate (250 or 300 kbs) has been selected DENSEL is active high for high density (525 drives)

when IDENT is high and active low for high density (35 drives) when IDENT is low DENSEL is also

programmable via the Mode command (see Section 426)

DIR

Direction

This output determines the direction of the floppy disk drive (FDD) head movement (active

step in inactive e step out) during a seek operation During read or writes DIR will be inactive

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