1
0
mirror of https://github.com/TomHarte/CLK.git synced 2024-12-24 12:30:17 +00:00

Adds support for the Blitter-busy flag to WAIT and SKIP.

This commit is contained in:
Thomas Harte 2021-11-27 11:36:15 -05:00
parent 33bfa1b81c
commit dac40630fd
3 changed files with 68 additions and 15 deletions

View File

@ -434,7 +434,7 @@ template <int cycle, bool stop_if_cpu> bool Chipset::perform_cycle() {
//
// The Blitter and CPU are dealt with outside of the odd/even test.
if((dma_control_ & CopperFlag) == CopperFlag) {
if(copper_.advance_dma(uint16_t(((y_ & 0xff) << 8) | (cycle & 0xfe)))) {
if(copper_.advance_dma(uint16_t(((y_ & 0xff) << 8) | (cycle & 0xfe)), blitter_.get_status())) {
return false;
}
} else {

View File

@ -18,13 +18,69 @@
using namespace Amiga;
bool Copper::advance_dma(uint16_t position) {
namespace {
bool satisfies_raster(uint16_t position, uint16_t blitter_status, uint16_t *instruction) {
const uint16_t mask = 0x8000 | (instruction[1] & 0x7ffe);
return
(position & mask) >= (instruction[0] & mask)
&& (!(blitter_status & 0x4000) || (instruction[1] & 0x8000));
}
}
//
// Quick notes on the Copper:
//
// There are three instructions: move, wait and skip.
//
// Move writes a value to one of the Chipset registers; it is encoded as:
//
// First word:
// b0: 0
// b1b8: register address
// b9+: unused ("should be set to 0")
//
// Second word:
// b0b15: value to move.
//
//
// Wait waits until the raster gets to at least a certain position, and
// optionally until the Blitter has finished. It is encoded as:
//
// First word:
// b0: 1
// b1b7: horizontal beam position
// b8+: vertical beam position
//
// Second word:
// b0: 0
// b1b7: horizontal beam comparison mask
// b8b14: vertical beam comparison mask
// b15: 1 => don't also wait for the Blitter to be finished; 0 => wait.
//
//
// Skip skips the next instruction if the raster has already reached a certain
// position, and optionally only if the Blitter has finished, and only if the
// next instruction is a move.
//
// First word:
// b0: 1
// b1b7: horizontal beam position
// b8+: vertical beam position
//
// Second word:
// b0: 1
// b1b7: horizontal beam comparison mask
// b8b14: vertical beam comparison mask
// b15: 1 => don't also wait for the Blitter to be finished; 0 => wait.
//
bool Copper::advance_dma(uint16_t position, uint16_t blitter_status) {
switch(state_) {
default: return false;
case State::Waiting:
// TODO: blitter-finished bit.
if((position & position_mask_) >= instruction_[0]) {
if(satisfies_raster(position, blitter_status, instruction_)) {
LOG("Unblocked waiting for " << PADHEX(4) << instruction_[0] << " at " << position);
state_ = State::FetchFirstWord;
}
@ -37,15 +93,16 @@ bool Copper::advance_dma(uint16_t position) {
break;
case State::FetchSecondWord: {
// Get and reset the should-skip-next flag.
const bool should_skip_move = skip_next_;
skip_next_ = false;
// Read in the second instruction word.
instruction_[1] = ram_[address_ & ram_mask_];
++address_;
// Check for a MOVE.
if(!(instruction_[0] & 1)) {
// A MOVE.
if(!should_skip_move) {
// Stop if this move would be a privilege violation.
instruction_[0] &= 0x1fe;
@ -70,21 +127,18 @@ bool Copper::advance_dma(uint16_t position) {
break;
}
// Prepare for a position comparison.
position_mask_ = 0x8001 | (instruction_[1] & 0x7ffe);
instruction_[0] &= position_mask_;
// Got to here => this is a WAIT or a SKIP.
if(!(instruction_[1] & 1)) {
// A WAIT. Just note that this is now waiting; the proper test
// will be applied from the next potential `advance` onwards.
// will be applied from the next potential `advance_dma` onwards.
state_ = State::Waiting;
break;
}
// Neither a WAIT nor a MOVE => a SKIP.
// TODO: blitter-finished bit.
skip_next_ = (position & position_mask_) >= instruction_[0];
skip_next_ = satisfies_raster(position, blitter_status, instruction_);
state_ = State::FetchFirstWord;
} break;
}

View File

@ -17,10 +17,10 @@ class Copper: public DMADevice<2> {
public:
using DMADevice<2>::DMADevice;
/// Offers a DMA slot to the Copper, specifying the current beam position.
/// Offers a DMA slot to the Copper, specifying the current beam position and Blitter status.
///
/// @returns @c true if the slot was used; @c false otherwise.
bool advance_dma(uint16_t position);
bool advance_dma(uint16_t position, uint16_t blitter_status);
/// Forces a reload of address @c id (i.e. 0 or 1) and restarts the Copper.
template <int id> void reload() {
@ -47,7 +47,6 @@ class Copper: public DMADevice<2> {
} state_ = State::Stopped;
bool skip_next_ = false;
uint16_t instruction_[2]{};
uint16_t position_mask_ = 0xffff;
};
}