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/* |
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* REU.cpp - 17xx REU emulation |
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* |
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* Frodo (C) 1994-1997,2002-2005 Christian Bauer |
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* |
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* This program is free software; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License as published by |
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* the Free Software Foundation; either version 2 of the License, or |
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* (at your option) any later version. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License |
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* along with this program; if not, write to the Free Software |
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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*/ |
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|
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/* |
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* Incompatibilities: |
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* ------------------ |
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* |
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* - REU interrupts are not emulated |
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* - Transfer time is not accounted for, all transfers |
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* are done in 0 cycles |
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*/ |
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|
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#include "sysdeps.h" |
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|
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#include "REU.h" |
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#include "CPUC64.h" |
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#include "Prefs.h" |
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|
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|
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/* |
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* Constructor |
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*/ |
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|
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REU::REU(MOS6510 *CPU) : the_cpu(CPU) |
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{ |
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int i; |
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|
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// Init registers |
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regs[0] = 0x40; |
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for (i=1; i<11; i++) |
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regs[i] = 0; |
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for (i=11; i<16; i++) |
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regs[i] = 0xff; |
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|
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ex_ram = NULL; |
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ram_size = ram_mask = 0; |
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|
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// Allocate RAM |
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open_close_reu(REU_NONE, ThePrefs.REUSize); |
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} |
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|
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|
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/* |
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* Destructor |
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*/ |
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|
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REU::~REU() |
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{ |
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// Free RAM |
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open_close_reu(ThePrefs.REUSize, REU_NONE); |
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} |
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|
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|
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/* |
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* Prefs may have changed, reallocate expansion RAM |
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*/ |
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|
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void REU::NewPrefs(Prefs *prefs) |
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{ |
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open_close_reu(ThePrefs.REUSize, prefs->REUSize); |
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} |
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|
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|
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/* |
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* Allocate/free expansion RAM |
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*/ |
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|
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void REU::open_close_reu(int old_size, int new_size) |
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{ |
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if (old_size == new_size) |
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return; |
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|
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// Free old RAM |
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if (old_size != REU_NONE) { |
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delete[] ex_ram; |
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ex_ram = NULL; |
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} |
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|
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// Allocate new RAM |
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if (new_size != REU_NONE) { |
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switch (new_size) { |
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case REU_128K: |
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ram_size = 0x20000; |
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break; |
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case REU_256K: |
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ram_size = 0x40000; |
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break; |
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case REU_512K: |
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ram_size = 0x80000; |
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break; |
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} |
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ram_mask = ram_size - 1; |
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ex_ram = new uint8[ram_size]; |
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|
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// Set size bit in status register |
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if (ram_size > 0x20000) |
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regs[0] |= 0x10; |
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else |
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regs[0] &= 0xef; |
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} |
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} |
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|
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|
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/* |
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* Reset the REU |
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*/ |
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|
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void REU::Reset(void) |
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{ |
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int i; |
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|
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for (i=1; i<11; i++) |
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regs[i] = 0; |
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for (i=11; i<16; i++) |
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regs[i] = 0xff; |
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|
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if (ram_size > 0x20000) |
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regs[0] = 0x50; |
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else |
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regs[0] = 0x40; |
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} |
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|
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|
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/* |
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* Read from REU register |
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*/ |
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|
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uint8 REU::ReadRegister(uint16 adr) |
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{ |
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if (ex_ram == NULL) |
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return rand(); |
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|
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switch (adr) { |
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case 0:{ |
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uint8 ret = regs[0]; |
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regs[0] &= 0x1f; |
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return ret; |
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} |
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case 6: |
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return regs[6] | 0xf8; |
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case 9: |
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return regs[9] | 0x1f; |
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case 10: |
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return regs[10] | 0x3f; |
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default: |
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return regs[adr]; |
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} |
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} |
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|
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|
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/* |
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* Write to REU register |
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*/ |
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|
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void REU::WriteRegister(uint16 adr, uint8 byte) |
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{ |
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if (ex_ram == NULL) |
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return; |
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|
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switch (adr) { |
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case 0: // Status register is read-only |
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case 11: // Unconnected registers |
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case 12: |
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case 13: |
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case 14: |
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case 15: |
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break; |
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case 1: // Command register |
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regs[1] = byte; |
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if ((byte & 0x90) == 0x90) |
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execute_dma(); |
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break; |
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default: |
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regs[adr] = byte; |
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break; |
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} |
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} |
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|
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|
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/* |
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* CPU triggered REU by writing to $ff00 |
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*/ |
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|
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void REU::FF00Trigger(void) |
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{ |
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if (ex_ram == NULL) |
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return; |
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|
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if ((regs[1] & 0x90) == 0x80) |
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execute_dma(); |
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} |
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|
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|
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/* |
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* Execute REU DMA transfer |
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*/ |
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|
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void REU::execute_dma(void) |
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{ |
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// Get C64 and REU transfer base addresses |
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uint16 c64_adr = regs[2] | (regs[3] << 8); |
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uint32 reu_adr = regs[4] | (regs[5] << 8) | (regs[6] << 16); |
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|
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// Calculate transfer length |
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int length = regs[7] | (regs[8] << 8); |
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if (!length) |
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length = 0x10000; |
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|
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// Calculate address increments |
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uint32 c64_inc = (regs[10] & 0x80) ? 0 : 1; |
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uint32 reu_inc = (regs[10] & 0x40) ? 0 : 1; |
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|
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// Do transfer |
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switch (regs[1] & 3) { |
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|
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case 0: // C64 -> REU |
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for (; length--; c64_adr+=c64_inc, reu_adr+=reu_inc) |
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ex_ram[reu_adr & ram_mask] = the_cpu->REUReadByte(c64_adr); |
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break; |
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|
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case 1: // C64 <- REU |
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for (; length--; c64_adr+=c64_inc, reu_adr+=reu_inc) |
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the_cpu->REUWriteByte(c64_adr, ex_ram[reu_adr & ram_mask]); |
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break; |
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|
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case 2: // C64 <-> REU |
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for (; length--; c64_adr+=c64_inc, reu_adr+=reu_inc) { |
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uint8 tmp = the_cpu->REUReadByte(c64_adr); |
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the_cpu->REUWriteByte(c64_adr, ex_ram[reu_adr & ram_mask]); |
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ex_ram[reu_adr & ram_mask] = tmp; |
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} |
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break; |
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|
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case 3: // Compare |
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for (; length--; c64_adr+=c64_inc, reu_adr+=reu_inc) |
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if (ex_ram[reu_adr & ram_mask] != the_cpu->REUReadByte(c64_adr)) { |
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regs[0] |= 0x20; |
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break; |
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} |
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break; |
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} |
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|
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// Update address and length registers if autoload is off |
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if (!(regs[1] & 0x20)) { |
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regs[2] = c64_adr; |
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regs[3] = c64_adr >> 8; |
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regs[4] = reu_adr; |
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regs[5] = reu_adr >> 8; |
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regs[6] = reu_adr >> 16; |
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regs[7] = length + 1; |
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regs[8] = (length + 1) >> 8; |
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} |
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|
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// Set complete bit in status register |
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regs[0] |= 0x40; |
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|
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// Clear execute bit in command register |
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regs[1] &= 0x7f; |
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} |
