Nibble mode: Not used

ECP mode: Bi-directional data

nACK/PtrClk/PeriphClk

All modes: DTA8 is the MSB, DATA1 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)

Busy/PtrBusy/PeriphClk

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.

A-8Technical Specifications