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4.2 Bidirectional Parallel Interface
Overview
The interface of the printer is a Level-1 compatible device according to IEEE-P1284. It supports the
communication modes described in 4.2.1 below.
4.2.1 Parallel Interface Communication Mode
The parallel interface of the printer provides three communication modes as outlined below. When the
printer is turned on or reset, it defaults to Compatibility mode.
• Compatibility Mode
Data is transmitted from the host to the printer in units of one byte. Usually, this mode is used for data
transmission. You may switch to the other modes from Compatibility mode.
• Nibble Mode
Data is transmitted from the printer to the host in units of four bits. The data transmission from the printer
uses a status signal line. To send one byte of data in this mode, two sets of four-bit data are sent consecutively.
• Byte Mode
Data is transmitted from the printer to the host in units of one byte. Data transmission from the printer
uses an 8-bit data signal line. For Byte mode, the host must be capable of toggling the signal direction over
the 8-bit data signal line. Communication from the host to the printer is called Forward mode, while
communication from the printer to the host is called Reverse mode.
4.2.2 Interfacing Phases
Interfacing in each communication mode is divided into several phases. In addition, there is a phase for
mode initialization, as well as a phase for mode switching. Interface signals may differ in name and function
for different modes and different phases.
*Forward
Data
Transfer
Forward
Idle
Reverse
Data
Transfer
Host Busy
Data Not
Available
Host Busy
Data
Available
Interrupt
Host
Reverse
Idle
Termination
Compatibility Mode
Negotiation
Failed
Negotiation
Event 1
Event 6 Event 6
Event 11
Event 7
Event 7 Event 21
Event 18
Event 11
Host Xmits
Data
Aborted
Transfer
Termination from
Other Modes
(Except EPP)
End forward
Data Xfer