From 95e00dd9580e06a516978f78f6731b16e682f8c4 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 27 Jan 2023 22:20:36 -0500
Subject: [PATCH] Take slightly wrong-headed steps towards proper command
timing.
---
Components/9918/Implementation/9918.cpp | 11 ++++++-
Components/9918/Implementation/9918Base.hpp | 32 +++++++++++++++++++++
2 files changed, 42 insertions(+), 1 deletion(-)
diff --git a/Components/9918/Implementation/9918.cpp b/Components/9918/Implementation/9918.cpp
index 3a0c9815e..5da9d04a0 100644
--- a/Components/9918/Implementation/9918.cpp
+++ b/Components/9918/Implementation/9918.cpp
@@ -159,7 +159,7 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
#endif
if(fetch_cycles_pool) {
- // Determine how much writing to do.
+ // Determine how much writing to do; at the absolute most go to the end of this line.
const int fetch_cycles = std::min(
Timing<personality>::CyclesPerLine - this->fetch_pointer_.column,
fetch_cycles_pool
@@ -171,6 +171,15 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
this->minimum_access_column_ = this->fetch_pointer_.column + this->cycles_until_access_;
this->cycles_until_access_ -= fetch_cycles;
+ // ... and to any pending Yamaha commands.
+ if constexpr (is_yamaha_vdp(personality)) {
+ if(Storage<personality>::command_) {
+ Storage<personality>::minimum_command_column_ =
+ this->fetch_pointer_.column + Storage<personality>::command_->cycles;
+ Storage<personality>::command_->cycles -= fetch_cycles;
+ }
+ }
+
// ---------------------------------------
// Latch scrolling position, if necessary.
diff --git a/Components/9918/Implementation/9918Base.hpp b/Components/9918/Implementation/9918Base.hpp
index 5032ebb64..d0f8a164b 100644
--- a/Components/9918/Implementation/9918Base.hpp
+++ b/Components/9918/Implementation/9918Base.hpp
@@ -187,6 +187,27 @@ template <Personality personality> struct Storage<personality, std::enable_if_t<
CommandContext command_context_;
std::unique_ptr<Command> command_ = nullptr;
+ enum class CommandStep {
+ None,
+ ReadPixel,
+ WritePixel,
+ };
+ CommandStep next_command_step_ = CommandStep::None;
+ int minimum_command_column_ = 0;
+
+ void update_command_step() {
+ if(!command_) {
+ next_command_step_ = CommandStep::None;
+ return;
+ }
+
+ switch(command_->access) {
+ case Command::AccessType::PlotPoint:
+ next_command_step_ = CommandStep::ReadPixel;
+ break;
+ }
+ }
+
Storage() noexcept {
// Perform sanity checks on the event lists.
#ifndef NDEBUG
@@ -552,6 +573,17 @@ template <Personality personality> struct Base: public Storage<personality> {
// Don't do anything if the required time for the access to become executable
// has yet to pass.
if(queued_access_ == MemoryAccess::None || access_column < minimum_access_column_) {
+ if constexpr (is_yamaha_vdp(personality)) {
+// if(
+// Storage<personality>::next_command_step_ == Storage<personality>::CommandStep::None ||
+// access_column < Storage<personality>::minimum_access_column_
+// ) {
+// return;
+// }
+
+ // TODO: command-engine action.
+ }
+
return;
}