16.022 A friend with Apple //c's and IIc+'s wants to connect them to RGB monitors. What is the //c/IIc+ video port pin configuration?
Description
This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
16.022 A friend with Apple //c's and IIc+'s wants to connect them to RGB monitors. What is the //c/IIc+ video port pin configuration?
First, I should correct a misconception: the video port on the back of the
IIc+ is not an RGB port. It is a video expansion port, which provides all of
the internal video generation signals used by the IIc/IIc+ which can be used to
generate an alternative video output signal.
The actual functions of the IIc video port are as follows:
1 TEXT Indicates text mode is active (spcl fn in DHR mode)
2 14M 14 MHz clock sigal
3 SYNC Horizontal and vertical sync
4 SEGB Vertical counter signal from IOU, or lo-res indication
5 1VSOUND Sound output (one volt peak-to-peak)
6 LDPS Video shift load enable
7 WNDW Active area display blanking
8 +12V +12 volts DC
9 PRAS RAM row address strobe
10 GR Graphics mode enable
11 SEROUT Serialized character generator output
12 NTSC Composite NTSC video output
13 GND Ground reference
14 VIDD7 Bit 7 of video shift latch (hires mode col shifting)
15 CREF Colour reference timing signal
These come from the IIc Technical Reference, both first and second editions.
You cannot connect a monitor directly to the IIc video port (with the
possible exception of the the LCD display, or an NTSC monitor). To produce RGB
output (or anything else) from this port, you need an external adapter box.
This adapter is not simple: it has to decode the colour information from
the NTSC video signal (or generate it by detecting the graphics mode and
monitoring bit patterns), generate appropriate sync signals, etc.
I believe there is (or was) an RGB output adapter for the IIc, which
should also work on the IIc+.
By: David Empson
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