From 36bfba32f7ca7320d949277b3ecf9b15a5f1ac18 Mon Sep 17 00:00:00 2001 From: AJR Date: Sun, 3 Nov 2019 22:03:25 -0500 Subject: st2xxx: Misc. notes (nw) --- src/devices/cpu/m6502/st2205u.cpp | 4 ++++ src/devices/cpu/m6502/st2xxx.cpp | 1 + 2 files changed, 5 insertions(+) diff --git a/src/devices/cpu/m6502/st2205u.cpp b/src/devices/cpu/m6502/st2205u.cpp index 2dff95733f0..0e2e17ce206 100644 --- a/src/devices/cpu/m6502/st2205u.cpp +++ b/src/devices/cpu/m6502/st2205u.cpp @@ -24,6 +24,10 @@ * 512K ROM (may be disabled) * 32K SRAM + One important difference between the ST2205U and almost every + other ST2XXX MCU is that PRR[0] and IRR[0] are *not* inverted + relative to A14. + **********************************************************************/ #include "emu.h" diff --git a/src/devices/cpu/m6502/st2xxx.cpp b/src/devices/cpu/m6502/st2xxx.cpp index 8905e9942d4..5748668b6c3 100644 --- a/src/devices/cpu/m6502/st2xxx.cpp +++ b/src/devices/cpu/m6502/st2xxx.cpp @@ -124,6 +124,7 @@ u8 st2xxx_device::pdata_r(offs_t offset) void st2xxx_device::pdata_w(offs_t offset, u8 data) { + // Set output state (CMOS or open drain) or activate/deactive pullups for input pins if (data != m_pdata[offset]) { m_pdata[offset] = data; -- cgit v1.2.3