diff options
Diffstat (limited to 'sid/sidplay-libs-2.1.0/libsidplay/src/mos656x/mos656x.cpp')
| -rw-r--r-- | sid/sidplay-libs-2.1.0/libsidplay/src/mos656x/mos656x.cpp | 256 |
1 files changed, 256 insertions, 0 deletions
diff --git a/sid/sidplay-libs-2.1.0/libsidplay/src/mos656x/mos656x.cpp b/sid/sidplay-libs-2.1.0/libsidplay/src/mos656x/mos656x.cpp new file mode 100644 index 00000000..a7e03642 --- /dev/null +++ b/sid/sidplay-libs-2.1.0/libsidplay/src/mos656x/mos656x.cpp @@ -0,0 +1,256 @@ +/*************************************************************************** + + mos656x.cpp - Minimal VIC emulation + ------------------- + begin : Wed May 21 2001 + copyright : (C) 2001 by Simon White + email : s_a_white@email.com + ***************************************************************************/ + +/*************************************************************************** + * * + * This program is free software; you can redistribute it and/or modify * + * it under the terms of the GNU General Public License as published by * + * the Free Software Foundation; either version 2 of the License, or * + * (at your option) any later version. * + * * + ***************************************************************************/ + +#include "sidendian.h" +#include "mos656x.h" + +#define MOS6567R56A_FIRST_DMA_LINE 0x30 +#define MOS6567R56A_LAST_DMA_LINE 0xf7 + +#define MOS6567R8_FIRST_DMA_LINE 0x30 +#define MOS6567R8_LAST_DMA_LINE 0xf7 + +#define MOS6569_FIRST_DMA_LINE 0x30 +#define MOS6569_LAST_DMA_LINE 0xff + +const char *MOS656X::credit = +{ // Optional information + "*MOS656X (VICII) Emulation:\0" + "\tCopyright (C) 2001 Simon White <sidplay2@email.com>\0" +}; + + +MOS656X::MOS656X (EventContext *context) +:Event("VIC Raster"), + event_context(*context) +{ + chip (MOS6569); +} + +void MOS656X::reset () +{ + icr = idr = ctrl1 = 0; + raster_irq = 0; + y_scroll = 0; + raster_y = yrasters - 1; + raster_x = xrasters - 1; + bad_lines_enabled = false; + event_context.schedule (this, 1); + m_accessClk = 0; +} + +void MOS656X::chip (mos656x_model_t model) +{ + switch (model) + { + // Seems to be an older NTSC chip + case MOS6567R56A: + yrasters = 262; + xrasters = 64; + first_dma_line = MOS6567R56A_FIRST_DMA_LINE; + last_dma_line = MOS6567R56A_LAST_DMA_LINE; + break; + + // NTSC Chip + case MOS6567R8: + yrasters = 263; + xrasters = 65; + first_dma_line = MOS6567R8_FIRST_DMA_LINE; + last_dma_line = MOS6567R8_LAST_DMA_LINE; + break; + + // PAL Chip + case MOS6569: + yrasters = 312; + xrasters = 63; + first_dma_line = MOS6569_FIRST_DMA_LINE; + last_dma_line = MOS6569_LAST_DMA_LINE; + break; + } + + reset (); +} + +uint8_t MOS656X::read (uint_least8_t addr) +{ + if (addr > 0x3f) return 0; + if (addr > 0x2e) return 0xff; + + switch (addr) + { + case 0x11: // Control register 1 + return (raster_y & 0x100) >> 1; + case 0x12: // Raster counter + return raster_y & 0xFF; + case 0x19: // IRQ flags + return idr; + case 0x1a: // IRQ mask + return icr | 0xf0; + default: return regs[addr]; + } +} + +void MOS656X::write (uint_least8_t addr, uint8_t data) +{ + if (addr > 0x3f) return; + + regs[addr] = data; + + switch (addr) + { + case 0x11: // Control register 1 + endian_16hi8 (raster_irq, data >> 7); + ctrl1 = data; + y_scroll = data & 7; + + if (raster_x < 11) + break; + + // In line $30, the DEN bit controls if Bad Lines can occur + if (raster_y == 0x30 && data & 0x10) + bad_lines_enabled = true; + + // Bad Line condition? + bad_line = (raster_y >= first_dma_line) && + (raster_y <= last_dma_line) && + ((raster_y & 7) == y_scroll) && + bad_lines_enabled; + + // Start DMA + if (bad_line && (raster_x < 54)) + { + busaccess(false); + if (raster_x < 52) + event_context.schedule (this, 3); + } + break; + + case 0x12: // Raster counter + endian_16lo8 (raster_irq, data); + break; + + case 0x19: // IRQ flags + idr &= ((~data & 0x0f) | 0x80); + if (idr == 0x80) + trigger (0); + break; + + case 0x1a: // IRQ mask + icr = data & 0x0f; + trigger (icr & idr); + break; + } +} + + +void MOS656X::trigger (int irq) +{ + if (!irq) + { // Clear any requested IRQs + if (idr & MOS656X_INTERRUPT_REQUEST) + interrupt (false); + idr = 0; + return; + } + + idr |= irq; + if (icr & idr) + { + if (!(idr & MOS656X_INTERRUPT_REQUEST)) + { + idr |= MOS656X_INTERRUPT_REQUEST; + interrupt (true); + } + } +} + +void MOS656X::event (void) +{ + event_clock_t delay = 1; + + switch (raster_x) + { + case 0: // IRQ occurred (xraster != 0) + if (raster_y != yrasters - 1) + { + raster_y++; + // Trigger raster IRQ if IRQ line reached + if (raster_y == raster_irq) + trigger (MOS656X_INTERRUPT_RST); + delay = 11; + } + break; + case 1: // Vertical blank (line 0) + // Trigger raster IRQ if IRQ in line 0 + raster_y = 0; + if (raster_y == raster_irq) + trigger (MOS656X_INTERRUPT_RST); + delay = 10; + break; + + case 11: // Start bad line + { // In line $30, the DEN bit controls if Bad Lines can occur + if (raster_y == first_dma_line) + bad_lines_enabled = (ctrl1 & 0x10) != 0; + + // Test for bad line condition + bad_line = (raster_y >= first_dma_line) && + (raster_y <= last_dma_line) && + ((raster_y & 7) == y_scroll) && + bad_lines_enabled; + + delay = xrasters - 11; + if (bad_line) + { + delay = 3; + busaccess (false); + } + break; + } + + case 14: // Start DMA + addrctrl (false); + delay = 40; + break; + case 54: // End DMA + busaccess (true); + addrctrl (true); + delay = xrasters - 54; + break; + + case 12: + case 13: + break; + + default: + if (bad_line && (raster_x < 54)) + { + addrctrl (false); + delay = 54 - raster_x; + } + else + { // Skip to the end of raster + busaccess (true); + delay = xrasters - raster_x; + } + } + + raster_x += delay; + raster_x %= xrasters; + event_context.schedule (this, delay); +} |