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Chapter
5
IEEE 1284 Parallel Interface
Byte Mode
The printer and host send data to each other along eight data lines (one bit
per line).
If bidirectional communication is supported by the printer and the host, the
host will take control of the data transfer.
The Negotiation Phase
The negotiation phase determines which operating mode will be used. At this
time, the host and the printer will sense what devices are attached, the
supported signals available, and which mode to use. The selected mode, in
turn, defines the pins on the 1284 connector.
There are 36 pins on the parallel interface. Each one sends a different signal.
Pin 1, for example, can send a Strobe signal or a HostC1k signal, depending
on the mode selected. See Table 10 for the different connector signals.
Signals
Table 10 lists each of the signals associated with the corresponding pins on
the 1284 interface. Descriptions of the signals follow.
Pin
Source of Data
1
2
Host/Printer
3
Host/Printer
4
Host/Printer
5
Host/Printer
6
Host/Printer
7
Host/Printer
8
Host/Printer
9
Host/Printer
10
11
12
13
260
Table 10. 1284 Signals
Compatible
Host
nStrobe
Data 1 (LSB)
Data 2
Data 3
Data 4
Data 5
Data 6
Data 7
Data 8 (MSB)
Printer
nAck
Printer
Busy
Printer
PError
Printer
Select
Type of Mode
Nibble
Byte
HostClk
Host/Clk
PtrClk
PtrClk
PtrBusy
PtrBusy
AckDataReq
AckDataReq
Xflag
Xflag
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