Browse Prior Art Database

Self-Initializing CRT Adapter for Multiple CRT Types

IP.com Disclosure Number: IPCOM000039547D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Landers, JD: AUTHOR

Abstract

This article describes a programmable CRT adapter which determines the type of monitor which is attached to it and generates appropriate signals for driving the monitor. The CRT adapter shown above includes a CRT controller (CRTC) which is a very large-scale integration (VLSI) vendor module. The module can be purchased off the shelf and generates timing signals necessary to drive logic that drives the CRT (not shown). The fundamental signals (for example, vertical sync, horizontal sync and video) that drive the CRT are all determined by the frequency outputted from the programmable (PROG) clock and the programming of the CRTC. The read/write (RW) control circuit driving this clock is a programmable divide-down circuit that gives up to six different base frequencies.

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Self-Initializing CRT Adapter for Multiple CRT Types

This article describes a programmable CRT adapter which determines the type of monitor which is attached to it and generates appropriate signals for driving the monitor. The CRT adapter shown above includes a CRT controller (CRTC) which is a very large-scale integration (VLSI) vendor module. The module can be purchased off the shelf and generates timing signals necessary to drive logic that drives the CRT (not shown). The fundamental signals (for example, vertical sync, horizontal sync and video) that drive the CRT are all determined by the frequency outputted from the programmable (PROG) clock and the programming of the CRTC. The read/write (RW) control circuit driving this clock is a programmable divide-down circuit that gives up to six different base frequencies. The multiplicity of different frequencies combined with the ability to program the CRTC to different values, based on the given frequency, gives a wide range of possible combinations of CRT timings. The ability to vary timings to such a large degree gives the ability to drive different types of CRTs with different display formats. Another aspect of this design is the ability to change the polarity of the horizontal and vertical synchronization pulses. These pulses are typically 2-5% duty-cycle pulses and are either positive or negative active depending on the particular CRT. The polarity of the outgoing signal is programmed by placing an exclusive OR gate (not shown...