From b668d1d3ca5b2f7b404d5b4ea86e83b2fc98d906 Mon Sep 17 00:00:00 2001 From: Vas Crabb Date: Wed, 15 Aug 2018 19:07:13 +1000 Subject: add note about C-A-A behaviour on A1200 keyboard (nw) --- src/devices/bus/amiga/keyboard/a2000.cpp | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/devices/bus/amiga/keyboard/a2000.cpp b/src/devices/bus/amiga/keyboard/a2000.cpp index b8739807889..c728c7a43ee 100644 --- a/src/devices/bus/amiga/keyboard/a2000.cpp +++ b/src/devices/bus/amiga/keyboard/a2000.cpp @@ -43,6 +43,15 @@ ceramic resonator, a TI SN74HC00N, and a Hitachi HD74HC123AP. The header for the host connection has four positions and pins. + When the third key of the Ctrl-Amiga-Amiga sequence is pressed, the + keyboard will pull CLOCK low for 272,007 machine cycles (680ms - a + normal CLOCK pulse is 4 machine cycles, or 10µs), followed by the + power-up code 0xFE 1,706 machine cycles (4.265ms) later. This is + repeated every 280,787 machine cycles (702ms) as long as the keys + are held. Supposedly if the host chipset detects CLOCK has been + pulled low for at least 60ms, it will generate a 250ms reset pulse + when CLOCK is released. + ***************************************************************************/ #include "emu.h" -- cgit v1.2.3