Re: German IIe Question and ROM/JEDEC Link

["David Wilson" <mcs6502@gmail.com>]

heuser.marcus@freenet.de wrote:
> By the way:
> The "keyboard switch" actually is a "video switch" - which means it
> only serves for deciding which character sets appears on screen. It
> does not switch between keyboard layouts but rather switches the
> optical representation of the key codes.
> This is done IIRC by switching +5V to the A12 line of the video ROM --
> the Apple actually doesn't "know" which character set is active so this
> is comletely transparent to the DOS or applications.

This is not coreect. On the PAL motherboard the keyboard switch affects
both the keyboard and video. See the circuit diagram on page 8-18 of
"Understanding the Apple IIe" by Jim Sather. The switch generates a
signal called ALTCHR' which is connected to A10 (pin 19) of the
keyboard ROM [2716] and to A12 (pin 2) of the video ROM [2764].

I know in the case of the UK version we got here in Australia with the
341-150-A keyboard ROM the two halves of the ROM are identical as the
only difference is that # is replaced with £ and both have exactly the
same code.

The US motherboard has the same sized keyboard ROM and has a Dvorak
layout in the 2nd half but no switch to select it (unlike the IIc).