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Amps up the documentation.

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This commit is contained in:
Thomas Harte 2019-11-17 21:28:51 -05:00
parent 25da8b7787
commit facc0a1976
2 changed files with 52 additions and 16 deletions
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8
Machines/Atari/ST/Video.cpp
View File

@ -33,7 +33,7 @@ const struct VerticalParams {
};
/// @returns The correct @c VerticalParams for output at @c frequency.
const VerticalParams &vertical_parameters(FieldFrequency frequency) {
const VerticalParams &vertical_parameters(Video::FieldFrequency frequency) {
return vertical_params[int(frequency)];
}
@ -63,7 +63,7 @@ const struct HorizontalParams {
{4*2, 164*2, 184*2, 2*2, 224*2}
};
const HorizontalParams &horizontal_parameters(FieldFrequency frequency) {
const HorizontalParams &horizontal_parameters(Video::FieldFrequency frequency) {
return horizontal_params[int(frequency)];
}
@ -72,14 +72,14 @@ struct Checker {
Checker() {
for(int c = 0; c < 3; ++c) {
// Expected horizontal order of events: reset blank, enable display, disable display, enable blank (at least 50 before end of line), end of line
const auto horizontal = horizontal_parameters(FieldFrequency(c));
const auto horizontal = horizontal_parameters(Video::FieldFrequency(c));
assert(horizontal.reset_blank < horizontal.set_enable);
assert(horizontal.set_enable < horizontal.reset_enable);
assert(horizontal.reset_enable < horizontal.set_blank);
assert(horizontal.set_blank+50 < horizontal.length);
// Expected vertical order of events: reset blank, enable display, disable display, enable blank (at least 50 before end of line), end of line
const auto vertical = vertical_parameters(FieldFrequency(c));
const auto vertical = vertical_parameters(Video::FieldFrequency(c));
assert(vertical.set_enable < vertical.reset_enable);
assert(vertical.reset_enable < vertical.height);
}

60
Machines/Atari/ST/Video.hpp
View File

@ -15,14 +15,20 @@
namespace Atari {
namespace ST {
enum class FieldFrequency {
Fifty = 0, Sixty = 1, SeventyTwo = 2
};
/*!
Models a combination of the parts of the GLUE, MMU and Shifter that in net
form the video subsystem of the Atari ST. So not accurate to a real chip, but
(hopefully) to a subsystem.
*/
class Video {
public:
Video();
/*!
Sets the memory pool that provides video, and its size.
*/
void set_ram(uint16_t *, size_t size);
/*!
Sets the target device for video data.
*/
@ -33,21 +39,51 @@ class Video {
*/
void run_for(HalfCycles duration);
/*!
@returns the number of cycles until there is next a change in the hsync,
vsync or display_enable outputs.
*/
HalfCycles get_next_sequence_point();
/*!
@returns @c true if the horizontal sync output is currently active; @c false otherwise.
@discussion On an Atari ST, this generates a VPA-style interrupt, which is often erroneously
documented as being triggered by horizontal blank.
*/
bool hsync();
/*!
@returns @c true if the vertical sync output is currently active; @c false otherwise.
@discussion On an Atari ST, this generates a VPA-style interrupt, which is often erroneously
documented as being triggered by vertical blank.
*/
bool vsync();
/*!
@returns @c true if the display enabled output is currently active; @c false otherwise.
@discussion On an Atari ST this is fed to the MFP. The documentation that I've been able to
find implies a total 28-cycle delay between the real delay enabled signal changing and its effect
on the 68000 interrupt input via the MFP. As I have yet to determine how much delay is caused
by the MFP a full 28-cycle delay is applied by this class. This should be dialled down when the
MFP's responsibility is clarified.
*/
bool display_enabled();
void set_ram(uint16_t *, size_t size);
/// @returns the effect of reading from @c address; only the low 6 bits are decoded.
uint16_t read(int address);
/// Writes @c value to @c address, of which only the low 6 bits are decoded.
void write(int address, uint16_t value);
/// Used internally to track state.
enum class FieldFrequency {
Fifty = 0, Sixty = 1, SeventyTwo = 2
};
private:
Outputs::CRT::CRT crt_;
@ -56,7 +92,7 @@ class Video {
int base_address_ = 0;
int current_address_ = 0;
uint16_t *ram_;
uint16_t *ram_ = nullptr;
uint16_t line_buffer_[256];
int x_ = 0, y_ = 0, next_y_ = 0;
@ -67,7 +103,7 @@ class Video {
FieldFrequency field_frequency_ = FieldFrequency::Fifty;
enum class OutputBpp {
One, Two, Four
} output_bpp_;
} output_bpp_ = OutputBpp::Four;
void update_output_mode();
struct HorizontalState {
@ -92,7 +128,7 @@ class Video {
int line_length_ = 1024;
int data_latch_position_ = 0;
uint16_t data_latch_[4];
uint16_t data_latch_[4] = {0, 0, 0, 0};
void latch_word();
class Shifter {
@ -110,8 +146,8 @@ class Video {
enum class OutputMode {
Sync, Blank, Border, Pixels
} output_mode_ = OutputMode::Sync;
uint16_t border_colour_;
OutputBpp bpp_;
uint16_t border_colour_ = 0;
OutputBpp bpp_ = OutputBpp::Four;
union {
uint64_t output_shifter_;
uint32_t shifter_halves_[2];
@ -119,7 +155,7 @@ class Video {
void flush_output(OutputMode next_mode);
uint16_t *pixel_buffer_;
uint16_t *pixel_buffer_ = nullptr;
size_t pixel_pointer_ = 0;
Outputs::CRT::CRT &crt_;