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

+5V

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 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. 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. 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 1284 Active (nSelectIn) is set high. 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 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. 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.