CD1284 datasheet(84/176 Pages) INTEL

84 / 176 page

CD1284 — IEEE 1284-Compatible Parallel Interface Controller

Datasheet

At reset, all bits in the GPIO are cleared and the signals are programmed as inputs.

Note:

Interrupts are not generated on signal changes within the General-Purpose I/O port; the CPU must

periodically poll GPIO to detect changes in external conditions. Therefore, if it is necessary to

detect changes, use the port with signals that change with low-duty cycles.

5.16

Parallel Port Interface

The CD1284 parallel port signals are implemented with Level 2 characteristics – as defined in the

IEEE STD 1284 specification with the exception of transient protection. The port can be directly

connected to the interface cable with the addition of a few external components. The components

consist of passive pull-up resistors, series-impedance-matching resistors, and clipping diodes.

Additional noise-filtering may be required in an end system. Figure 13 on page 85 shows a typical

interface with the components listed above.

Some system designs may require buffers between the CD1284 and the cable. Systems that require

drive cables longer than the specified maximum of 10 m or those that need to protect the CD1284

require inexpensive buffers between it and the cable. The device provides two signal outputs,

PDBEN and EBDIR, that can to connect and control buffers (such as, 74AS245 or equivalent).

These signals do not allow direct control of the buffer. However, the addition of an XNOR gate

provides both an enable control signal and a signal to select the direction of the buffer. PDBEN and

EBDIR are outputs from the control state machine that indicate its current state (see Figure 14 on

page 86).

CD1284 Datasheet(PDF) 84 Page - Intel Corporation