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Transcribe some timing numbers.

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This commit is contained in:
Thomas Harte 2024-12-10 22:56:14 -05:00
parent 38325741de
commit aed8f8efa8
2 changed files with 70 additions and 4 deletions
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8
Machines/Commodore/Plus4/Plus4.cpp
View File

@ -130,11 +130,11 @@ public:
ConcreteMachine(const Analyser::Static::Commodore::Target &target, const ROMMachine::ROMFetcher &rom_fetcher) :
m6502_(*this)
{
// PAL: 8'867'240 divided by 5 or 4?
// NTSC: 7'159'090?
// PAL: 8867240 divided by 5 or 4?
// NTSC: 7159090?
// i.e. colour subcarriers multiplied by two?
set_clock_rate(8'867'240); // TODO.
set_clock_rate(7159090); // TODO.
const auto kernel = ROM::Name::Plus4KernelPALv5;
const auto basic = ROM::Name::Plus4BASIC;
@ -171,6 +171,8 @@ public:
const auto timers_cycles = timers_subcycles_.divide(Cycles(5));
timers_.tick(timers_cycles.as<int>());
video_.run_for(length);
// Perform actual access.
if(address < 0xfd00 || address >= 0xff40) {
if(isReadOperation(operation)) {

66
Machines/Commodore/Plus4/Video.hpp
View File

@ -25,7 +25,6 @@ public:
);
};
switch(address) {
case 0xff06:
extended_colour_mode_ = value & 0x40;
@ -58,6 +57,68 @@ public:
}
}
// Outer clock is [NTSC or PAL] colour subcarrier * 2.
//
// 65 cycles = 64µs?
// 65*262*60 = 1021800
//
// In an NTSC television system. 262 raster lines are produced (0 to 261), 312 for PAL (0−311).
//
// An interrupt is generated 8 cycles before the character window. For a 25 row display, the visible
// raster lines are from 4 to 203.
//
// The horizontal position register counts 456 dots, 0 to 455.
void run_for(Cycles) {
// Timing:
//
// 456 cycles/line;
// if in PAL mode, divide input clock by 1.25 (?);
// see page 34 of plus4_tech.pdf for event times.
// Horizontal events:
//
// 3: 38-column screen start
// 288: external fetch window end, refresh single clock start, increment character position end
// 290: latch character position to reload
// 296: character window end, character window single clock end, increment refresh start
// 304: video shift register end
// 307: 38-column screen stop
// 315: 40-column screen end
// 328: refresh single clock end
// 336: increment blink, increment refresh end
// 344: horizontal blanking start
// 358: horizontal sync start
// 376: increment vertical line
// 384: burst start, end of screen — clear vertical line, vertical sub and character reload registers
// 390: horizontal sync end
// 408: burst end
// 400: external fetch window start
// 416: horizontal blanking end
// 424: increment character position reload
// 432: character window start, character window single clock start, increment character position start
// 440: video shift register start
// 451: 40-column screen start
// Vertical events:
//
// 0: attribute fetch start
// 4: vertical screen window start (25 lines)
// 8: vertical screen window start (24 lines)
// 203: attribute fetch end
// 200: vertical screen window stop (24 lines)
// 204: frame window stop, vertical screen window stop (25 lines)
// 226: NTSC vertical blank start
// 229: NTSC vsync start
// 232: NTSC vsync end
// 244: NTSC vertical blank end
// 251: PAL vertical blank start
// 254: PAL vsync start
// 257: PAL vsync end
// 261: end of screen NTSC
// 269: PAL vertical blank end
// 311: end of screen PAL
}
private:
bool extended_colour_mode_ = false;
bool bitmap_mode_ = false;
@ -76,6 +137,9 @@ private:
uint16_t character_row_address_ = 0;
uint16_t character_generator_address_ = 0;
uint16_t screen_memory_address_ = 0;
int horizontal_counter_ = 0;
int vertical_counter_ = 0;
};
}