From f8380d2d4c4a2a6d78b4c5d3f99fa21208052b03 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 8 Aug 2021 22:32:41 -0400
Subject: [PATCH] Add 8250 feature of 'count, regardless'.

---
 Components/6526/Implementation/6526Implementation.hpp |  8 ++++----
 Components/6526/Implementation/6526Storage.hpp        | 11 +++++++++--
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/Components/6526/Implementation/6526Implementation.hpp b/Components/6526/Implementation/6526Implementation.hpp
index dabdbf353..46eb3ef81 100644
--- a/Components/6526/Implementation/6526Implementation.hpp
+++ b/Components/6526/Implementation/6526Implementation.hpp
@@ -79,10 +79,10 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
 		break;
 
 		// Counters; writes set the reload values.
-		case 4:		counter_[0].template set_reload<0>(value);	break;
-		case 5:		counter_[0].template set_reload<8>(value);	break;
-		case 6:		counter_[1].template set_reload<0>(value);	break;
-		case 7:		counter_[1].template set_reload<8>(value);	break;
+		case 4:		counter_[0].template set_reload<0, personality == Personality::P8250>(value);	break;
+		case 5:		counter_[0].template set_reload<8, personality == Personality::P8250>(value);	break;
+		case 6:		counter_[1].template set_reload<0, personality == Personality::P8250>(value);	break;
+		case 7:		counter_[1].template set_reload<8, personality == Personality::P8250>(value);	break;
 
 		// Time-of-day clock.
 		case 8:		tod_.template write<0>(value);	break;
diff --git a/Components/6526/Implementation/6526Storage.hpp b/Components/6526/Implementation/6526Storage.hpp
index cb3277d23..d193e87b2 100644
--- a/Components/6526/Implementation/6526Storage.hpp
+++ b/Components/6526/Implementation/6526Storage.hpp
@@ -189,12 +189,19 @@ struct MOS6526Storage {
 		uint16_t value = 0;
 		uint8_t control = 0;
 
-		template <int shift> void set_reload(uint8_t v) {
+		template <int shift, bool is_8250> void set_reload(uint8_t v) {
 			reload = (reload & (0xff00 >> shift)) | uint16_t(v << shift);
 
 			if constexpr (shift == 8) {
-				if(!(control&1)) {
+				// This seems to be a special 8250 feature per the Amiga
+				// Hardware Reference Manual; cf. Appendix F.
+				if(is_8250) {
+					control |= 1;
 					pending |= ReloadInOne;
+				} else {
+					if(!(control&1)) {
+						pending |= ReloadInOne;
+					}
 				}
 			}