Interface

Pin No.

Direction

IEEE 1284-B connector

Compatibility

Nibble

ECP

1

IN

nStorbe

HostClk

2

IN/OUT

DATA1

3

IN/OUT

DATA2

4

IN/OUT

DATA3

5

IN/OUT

DATA4

6

IN/OUT

DATA5

7

IN/OUT

DATA6

8

IN/OUT

DATA7

9

IN/OUT

DATA8

10

OUT

nACK

PtrClk

PeriphClk

11

OUT

Busy

PrtBusy

PeriphAck

12

OUT

PError

AckDataReq

nAckReverse

13

OUT

Select

Xflag

14

IN

nAutoFd

HostBusy

HostAck

15

NC

16

GND

17

CG

18

OUT

PeripheralLogic High

19 - 30

GND

31

IN

nlnit

nReverse Request

32

OUT

nFault

nDataAvail

nPeriphRequest

33

GND

34

NC

35

OUT

+5 Vdc

36

IN

nSelectln

IEEE1284 Active

Compatibility mode

Latch pulse used to read in print data. When low, DATA is valid.

Negotiation phase

Latch pulse used to read in extensibility request values

Nibble mode

Always high

ECP mode

Used to transfer data and addresses from the host to the printer with handshaking via PeriphAck (Busy)

Compatibility mode

Forward channel data

Negotiation phase

Extensibility request value

Nibble mode

Not used

ECP mode

Bidirectional data

All modes

DATA 8 is the MSB, DATA 1 is the LSB.

Compatibility mode

Acknowledgment low pulse in order to indicate that data was transferred from the host.

Negotiation phase

Low signal indicates IEEE 1284 is supported; set to high afterwards to indicate that the Xflag and "data available" flag are valid.

Reverse data transfer phase

In nibble mode, a low signal indicates that the nibble data is valid.

Reverse idle phase

When switched from low to high, generates an interrupt that notifies the host that there is data available.

ECP mode

Used to transfer data from the printer to the host with handshaking via HostAck (nAutoFd).

Compatibility mode

High signal indicates that the printer is not ready to receive data.

Negotiation phase

Reflects the BUSY status of the forward channel.

Reverse data transfer phase

In nibble mode, this signal serves as nibble data bit 3 and then 7.

Reverse idle phase

Reflects the BUSY status of the forward channel.

ECP mode

Used for forward direction flow control. In reverse direction, this signal is used as a ninth data bit that indicates whether the data signals indicate a command or data.

Compatibility mode

High signal indicates that a feed jam occurred in the paper supply section, or that there is no paper in the paper tray.

Negotiation phase

High signal indicates whether or not IEEE 1284 is supported or not. Afterwards, this signal conforms with nDataAvail (nFault).

Reverse data transfer phase

In nibble mode, this signal serves as nibble data bit 2 and then 6.

Reverse final phase

High, until the host requests a data transfer. Afterwards, this signal conforms with nDataAvail (nFault).

ECP mode

Low signal authorizes nReverseRequest. The host looks at this signal in order to determine whether or not it has permission to drive the data signals.

Compatibility mode

Always high.

Negotiation phase

Xflag indicates the extensibility flag. Used to respond to the extensibility request value sent from the host.

Reverse data transfer phase

In nibble mode, this signal serves as nibble data bit 1 and then 5.

Reverse idle phase

Same as negotiation phase.

ECP mode

Same as negotiation phase.

Compatibility mode

Not used.

Negotiation phase

In order to request 1284 mode, this signal is set low and IEEE 1284active (nSelectIn) is set high. Afterwards, this signal is set high when PtrClk (nAck) is set low.

Reverse data transfer phase

In nibble mode, setting this signal low indicates to the printer that the host is ready to receive data. When this signal is subsequently set high, it indicates that the host received the data.

Reverse idle phase

This signal is set high in response to a PtrClk (nAck) low pulse in order to return to reverse data phase. If this signal is set high at the same time that IEEE 1284 Active (nSelectIn) is set low, the IEEE 1284 idle phase is aborted and the interface returns to compatibility mode.

ECP mode

Used for reverse direction flow control. Also used for handshaking via PeriphClk (nAck).

Compatibility mode

When a low signal is detected, the printer is deemed to be BUSY until the low signal is released.

Negotiation phase

Always high

Reverse data transfer phase

Always high

ECP mode

Low when switching to reverse direction. The peripheral device has permission to drive the data signal only when this signal is low and 1284 active is high.

Compatibility mode

Low signal indicates that an error occurred.

Negotiation phase

This signal is set high in order to authorize 1284 compatibility. In nibble mode, after the host sets HostBusy (nAutoFd) high, this signal is set low in order to indicate that the transmission data is ready.

Reverse data transfer phase

This signal is set low in order to indicate to a nibble mode host that the transmission data is ready. Afterwards, this signal serves as nibble data bit 0 and then 4.

Reverse final phase

Indicates whether or not the data is valid.

ECP mode

This signal is set low to request communications with the host. Valid in both forward and reverse direction.

Compatibility mode

Always low.

Negotiation phase

This signal is set high at the same time that HostBusy is low in order to request 1284 mode.

Reverse data transfer phase

This signal is set high to indicate that the bus direction is from the printer to the host. This signal is set low to terminate 1284 mode, setting the bus direction from the host to the printer.

Reverse idle phase

Same as reverse data transfer phase.

ECP mode

Always high. This signal is set low to terminate ECP mode and return to compatibility mode.