From 5c94d0fce73c769faffd659da70e446ec2679f3e Mon Sep 17 00:00:00 2001 From: Thomas Harte Date: Fri, 17 Apr 2026 22:51:00 -0400 Subject: [PATCH] Add line-zeroing. --- Machines/Thomson/MO/MO.cpp | 3 +++ 1 file changed, 3 insertions(+) diff --git a/Machines/Thomson/MO/MO.cpp b/Machines/Thomson/MO/MO.cpp index 3281c1cbf..1426ce02b 100644 --- a/Machines/Thomson/MO/MO.cpp +++ b/Machines/Thomson/MO/MO.cpp @@ -371,6 +371,9 @@ private: } if constexpr (port == Motorola::MC6821::Port::B) { + // Cf. R118, R119 and T21 from the schematic; if PA3 (stored here as bit 6) is active then + // the output of PB1–3 (here bits 0 to 2) is ineffective. + const auto key = key_ & 0x40 ? key_ & ~7 : key_; return key_states_[key_] ? 0x00 : 0x80; }