Centronics Printer Interface
Control Port
The Control Port register has four input/output signals:
1.
Select In (SLIN*)
2.
Initialize (INIT*)
3.
Autofeed (AFD*)
4.
Strobe (STB*)
The Control Port register also contains an interrupt request enable bit,
IRQ ENB, which is an internal control signal. All I/O signals are
inverted at the frontplane except INIT*. This means that for all
Control Port signals except INIT* and IRQ ENB, writing a logical 1
to the register drives a logical 0 to the frontplane connector J6. All
four signals are also open-collector, so that a 1 must be written to the
Control register bit corresponding to the particular signal(s) being
used for input. Remember that an asterisk after the signal name
represents the signal’s active state at the printer interface.
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