Gravis Ultrasound GF1 sound card emulation (malc).

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3921 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 554 insertions, 0 deletions

diff --git a/hw/gusemu_hal.c b/hw/gusemu_hal.c
new file mode 100644
index 0000000000..c6f9537483
--- /dev/null
+++ b/hw/gusemu_hal.c
@@ -0,0 +1,554 @@
+/*
+ * GUSEMU32 - bus interface part
+ *
+ * Copyright (C) 2000-2007 Tibor "TS" Schütz
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/*
+ * TODO: check mixer: see 7.20 of sdk for panning pos (applies to all gus models?)?
+ */
+
+#include "gustate.h"
+#include "gusemu.h"
+
+#define GUSregb(position) (*            (gusptr+(position)))
+#define GUSregw(position) (*(GUSword *) (gusptr+(position)))
+#define GUSregd(position) (*(GUSdword *)(gusptr+(position)))
+
+/* size given in bytes */
+unsigned int gus_read(GUSEmuState * state, int port, int size)
+{
+    int             value_read = 0;
+
+    GUSbyte        *gusptr;
+    gusptr = state->gusdatapos;
+    GUSregd(portaccesses)++;
+
+    switch (port & 0xff0f)
+    {
+        /* MixerCtrlReg (read not supported on GUS classic) */
+        /* case 0x200: return GUSregb(MixerCtrlReg2x0); */
+    case 0x206:                          /* IRQstatReg / SB2x6IRQ */
+        /* adlib/sb bits set in port handlers */
+        /* timer/voice bits set in gus_irqgen() */
+        /* dma bit set in gus_dma_transferdata */
+        /* midi not implemented yet */
+        return GUSregb(IRQStatReg2x6);
+    /* case 0x308:                       */ /* AdLib388 */
+    case 0x208:
+        if (GUSregb(GUS45TimerCtrl) & 1)
+            return GUSregb(TimerStatus2x8);
+        return GUSregb(AdLibStatus2x8);  /* AdLibStatus */
+    case 0x309:                          /* AdLib389 */
+    case 0x209:
+        return GUSregb(AdLibData2x9);    /* AdLibData */
+    case 0x20A:
+        return GUSregb(AdLibCommand2xA); /* AdLib2x8_2xA */
+
+#if 0
+    case 0x20B:                          /* GUS hidden registers (read not supported on GUS classic) */
+        switch (GUSregb(RegCtrl_2xF) & 0x07)
+        {
+        case 0:                                 /* IRQ/DMA select */
+            if (GUSregb(MixerCtrlReg2x0) & 0x40)
+                return GUSregb(IRQ_2xB);        /* control register select bit */
+            else
+                return GUSregb(DMA_2xB);
+            /* case 1-5:                        */ /* general purpose emulation regs  */
+            /*  return ...                      */ /* + status reset reg (write only) */
+        case 6:
+            return GUSregb(Jumper_2xB);         /* Joystick/MIDI enable (JumperReg) */
+        default:;
+        }
+        break;
+#endif
+
+    case 0x20C:                          /* SB2xCd */
+        value_read = GUSregb(SB2xCd);
+        if (GUSregb(StatRead_2xF) & 0x20)
+            GUSregb(SB2xCd) ^= 0x80; /* toggle MSB on read */
+        return value_read;
+        /* case 0x20D:                   */ /* SB2xD is write only -> 2xE writes to it*/
+    case 0x20E:
+        if (GUSregb(RegCtrl_2xF) & 0x80) /* 2xE read IRQ enabled? */
+        {
+            GUSregb(StatRead_2xF) |= 0x80;
+            GUS_irqrequest(state, state->gusirq, 1);
+        }
+        return GUSregb(SB2xE);           /* SB2xE */
+    case 0x20F:                          /* StatRead_2xF */
+        /*set/clear fixed bits */
+        /*value_read = (GUSregb(StatRead_2xF) & 0xf9)|1; */ /*(LSB not set on GUS classic!)*/
+        value_read = (GUSregb(StatRead_2xF) & 0xf9);
+        if (GUSregb(MixerCtrlReg2x0) & 0x08)
+            value_read |= 2;    /* DMA/IRQ enabled flag */
+        return value_read;
+    /* case 0x300:                      */ /* MIDI (not implemented) */
+    /* case 0x301:                      */ /* MIDI (not implemented) */
+    case 0x302:
+        return GUSregb(VoiceSelReg3x2); /* VoiceSelReg */
+    case 0x303:
+        return GUSregb(FunkSelReg3x3);  /* FunkSelReg */
+    case 0x304:                         /* DataRegLoByte3x4 + DataRegWord3x4 */
+    case 0x305:                         /* DataRegHiByte3x5 */
+        switch (GUSregb(FunkSelReg3x3))
+        {
+    /* common functions */
+        case 0x41:                      /* DramDMAContrReg */
+            value_read = GUSregb(GUS41DMACtrl); /* &0xfb */
+            GUSregb(GUS41DMACtrl) &= 0xbb;
+            if (state->gusdma >= 4)
+                value_read |= 0x04;
+            if (GUSregb(IRQStatReg2x6) & 0x80)
+            {
+                value_read |= 0x40;
+                GUSregb(IRQStatReg2x6) &= 0x7f;
+                if (!GUSregb(IRQStatReg2x6))
+                    GUS_irqclear(state, state->gusirq);
+            }
+            return (GUSbyte) value_read;
+            /* DramDMAmemPosReg */
+            /* case 0x42: value_read=GUSregw(GUS42DMAStart); break;*/
+            /* 43h+44h write only */
+        case 0x45:
+            return GUSregb(GUS45TimerCtrl);         /* TimerCtrlReg */
+            /* 46h+47h write only */
+            /* 48h: samp freq - write only */
+        case 0x49:
+            return GUSregb(GUS49SampCtrl) & 0xbf;   /* SampCtrlReg */
+        /* case 4bh:                                */ /* joystick trim not supported */
+        /* case 0x4c: return GUSregb(GUS4cReset);   */ /* GUSreset: write only*/
+    /* voice specific functions */
+        case 0x80:
+        case 0x81:
+        case 0x82:
+        case 0x83:
+        case 0x84:
+        case 0x85:
+        case 0x86:
+        case 0x87:
+        case 0x88:
+        case 0x89:
+        case 0x8a:
+        case 0x8b:
+        case 0x8c:
+        case 0x8d:
+            {
+                int             offset = 2 * (GUSregb(FunkSelReg3x3) & 0x0f);
+                offset += ((int) GUSregb(VoiceSelReg3x2) & 0x1f) << 5; /* = Voice*32 + Funktion*2 */
+                value_read = GUSregw(offset);
+            }
+            break;
+    /* voice unspecific functions */
+        case 0x8e:                                  /* NumVoice */
+            return GUSregb(NumVoices);
+        case 0x8f:                                  /* irqstatreg */
+            /* (pseudo IRQ-FIFO is processed during a gus_write(0x3X3,0x8f)) */
+            return GUSregb(SynVoiceIRQ8f);
+        default:
+            return 0xffff;
+        }
+        if (size == 1)
+        {
+            if ((port & 0xff0f) == 0x305)
+                value_read = value_read >> 8;
+            value_read &= 0xff;
+        }
+        return (GUSword) value_read;
+    /* case 0x306:                                  */ /* Mixer/Version info */
+        /*  return 0xff; */ /* Pre 3.6 boards, ICS mixer NOT present */
+    case 0x307:                                     /* DRAMaccess */
+        {
+            GUSbyte        *adr;
+            adr = state->himemaddr + (GUSregd(GUSDRAMPOS24bit) & 0xfffff);
+            return *adr;
+        }
+    default:;
+    }
+    return 0xffff;
+}
+
+void gus_write(GUSEmuState * state, int port, int size, unsigned int data)
+{
+    GUSbyte        *gusptr;
+    gusptr = state->gusdatapos;
+    GUSregd(portaccesses)++;
+
+    switch (port & 0xff0f)
+    {
+    case 0x200:                 /* MixerCtrlReg */
+        GUSregb(MixerCtrlReg2x0) = (GUSbyte) data;
+        break;
+    case 0x206:                 /* IRQstatReg / SB2x6IRQ */
+        if (GUSregb(GUS45TimerCtrl) & 0x20) /* SB IRQ enabled? -> set 2x6IRQ bit */
+        {
+            GUSregb(TimerStatus2x8) |= 0x08;
+            GUSregb(IRQStatReg2x6) = 0x10;
+            GUS_irqrequest(state, state->gusirq, 1);
+        }
+        break;
+    case 0x308:                /* AdLib 388h */
+    case 0x208:                /* AdLibCommandReg */
+        GUSregb(AdLibCommand2xA) = (GUSbyte) data;
+        break;
+    case 0x309:                /* AdLib 389h */
+    case 0x209:                /* AdLibDataReg */
+        if ((GUSregb(AdLibCommand2xA) == 0x04) && (!(GUSregb(GUS45TimerCtrl) & 1))) /* GUS auto timer mode enabled? */
+        {
+            if (data & 0x80)
+                GUSregb(TimerStatus2x8) &= 0x1f; /* AdLib IRQ reset? -> clear maskable adl. timer int regs */
+            else
+                GUSregb(TimerDataReg2x9) = (GUSbyte) data;
+        }
+        else
+        {
+            GUSregb(AdLibData2x9) = (GUSbyte) data;
+            if (GUSregb(GUS45TimerCtrl) & 0x02)
+            {
+                GUSregb(TimerStatus2x8) |= 0x01;
+                GUSregb(IRQStatReg2x6) = 0x10;
+                GUS_irqrequest(state, state->gusirq, 1);
+            }
+        }
+        break;
+    case 0x20A:
+        GUSregb(AdLibStatus2x8) = (GUSbyte) data;
+        break;                 /* AdLibStatus2x8 */
+    case 0x20B:                /* GUS hidden registers */
+        switch (GUSregb(RegCtrl_2xF) & 0x7)
+        {
+        case 0:
+            if (GUSregb(MixerCtrlReg2x0) & 0x40)
+                GUSregb(IRQ_2xB) = (GUSbyte) data; /* control register select bit */
+            else
+                GUSregb(DMA_2xB) = (GUSbyte) data;
+            break;
+            /* case 1-4: general purpose emulation regs */
+        case 5:                                    /* clear stat reg 2xF */
+            GUSregb(StatRead_2xF) = 0; /* ToDo: is this identical with GUS classic? */
+            if (!GUSregb(IRQStatReg2x6))
+                GUS_irqclear(state, state->gusirq);
+            break;
+        case 6:                                    /* Jumper reg (Joystick/MIDI enable) */
+            GUSregb(Jumper_2xB) = (GUSbyte) data;
+            break;
+        default:;
+        }
+        break;
+    case 0x20C:                /* SB2xCd */
+        if (GUSregb(GUS45TimerCtrl) & 0x20)
+        {
+            GUSregb(TimerStatus2x8) |= 0x10; /* SB IRQ enabled? -> set 2xCIRQ bit */
+            GUSregb(IRQStatReg2x6) = 0x10;
+            GUS_irqrequest(state, state->gusirq, 1);
+        }
+    case 0x20D:                /* SB2xCd no IRQ */
+        GUSregb(SB2xCd) = (GUSbyte) data;
+        break;
+    case 0x20E:                /* SB2xE */
+        GUSregb(SB2xE) = (GUSbyte) data;
+        break;
+    case 0x20F:
+        GUSregb(RegCtrl_2xF) = (GUSbyte) data;
+        break;                 /* CtrlReg2xF */
+    case 0x302:                /* VoiceSelReg */
+        GUSregb(VoiceSelReg3x2) = (GUSbyte) data;
+        break;
+    case 0x303:                /* FunkSelReg */
+        GUSregb(FunkSelReg3x3) = (GUSbyte) data;
+        if ((GUSbyte) data == 0x8f) /* set irqstatreg, get voicereg and clear IRQ */
+        {
+            int             voice;
+            if (GUSregd(voicewavetableirq)) /* WavetableIRQ */
+            {
+                for (voice = 0; voice < 31; voice++)
+                {
+                    if (GUSregd(voicewavetableirq) & (1 << voice))
+                    {
+                        GUSregd(voicewavetableirq) ^= (1 << voice); /* clear IRQ bit */
+                        GUSregb(voice << 5) &= 0x7f; /* clear voice reg irq bit */
+                        if (!GUSregd(voicewavetableirq))
+                            GUSregb(IRQStatReg2x6) &= 0xdf;
+                        if (!GUSregb(IRQStatReg2x6))
+                            GUS_irqclear(state, state->gusirq);
+                        GUSregb(SynVoiceIRQ8f) = voice | 0x60; /* (bit==0 => IRQ wartend) */
+                        return;
+                    }
+                }
+            }
+            else if (GUSregd(voicevolrampirq)) /* VolRamp IRQ */
+            {
+                for (voice = 0; voice < 31; voice++)
+                {
+                    if (GUSregd(voicevolrampirq) & (1 << voice))
+                    {
+                        GUSregd(voicevolrampirq) ^= (1 << voice); /* clear IRQ bit */
+                        GUSregb((voice << 5) + VSRVolRampControl) &= 0x7f; /* clear voice volume reg irq bit */
+                        if (!GUSregd(voicevolrampirq))
+                            GUSregb(IRQStatReg2x6) &= 0xbf;
+                        if (!GUSregb(IRQStatReg2x6))
+                            GUS_irqclear(state, state->gusirq);
+                        GUSregb(SynVoiceIRQ8f) = voice | 0x80; /* (bit==0 => IRQ wartend) */
+                        return;
+                    }
+                }
+            }
+            GUSregb(SynVoiceIRQ8f) = 0xe8; /* kein IRQ wartet */
+        }
+        break;
+    case 0x304:
+    case 0x305:
+        {
+            GUSword         writedata = (GUSword) data;
+            GUSword         readmask = 0x0000;
+            if (size == 1)
+            {
+                readmask = 0xff00;
+                writedata &= 0xff;
+                if ((port & 0xff0f) == 0x305)
+                {
+                    writedata = (GUSword) (writedata << 8);
+                    readmask = 0x00ff;
+                }
+            }
+            switch (GUSregb(FunkSelReg3x3))
+            {
+                /* voice specific functions */
+            case 0x00:
+            case 0x01:
+            case 0x02:
+            case 0x03:
+            case 0x04:
+            case 0x05:
+            case 0x06:
+            case 0x07:
+            case 0x08:
+            case 0x09:
+            case 0x0a:
+            case 0x0b:
+            case 0x0c:
+            case 0x0d:
+                {
+                    int             offset;
+                    if (!(GUSregb(GUS4cReset) & 0x01))
+                        break;  /* reset flag active? */
+                    offset = 2 * (GUSregb(FunkSelReg3x3) & 0x0f);
+                    offset += (GUSregb(VoiceSelReg3x2) & 0x1f) << 5; /*  = Voice*32 + Funktion*2 */
+                    GUSregw(offset) = (GUSword) ((GUSregw(offset) & readmask) | writedata);
+                }
+                break;
+                /* voice unspecific functions */
+            case 0x0e:         /* NumVoices */
+                GUSregb(NumVoices) = (GUSbyte) data;
+                break;
+            /* case 0x0f:      */ /* read only */
+                /* common functions */
+            case 0x41:         /* DramDMAContrReg */
+                GUSregb(GUS41DMACtrl) = (GUSbyte) data;
+                if (data & 0x01)
+                    GUS_dmarequest(state);
+                break;
+            case 0x42:         /* DramDMAmemPosReg */
+                GUSregw(GUS42DMAStart) = (GUSregw(GUS42DMAStart) & readmask) | writedata;
+                GUSregb(GUS50DMAHigh) &= 0xf; /* compatibility stuff... */
+                break;
+            case 0x43:         /* DRAMaddrLo */
+                GUSregd(GUSDRAMPOS24bit) =
+                    (GUSregd(GUSDRAMPOS24bit) & (readmask | 0xff0000)) | writedata;
+                break;
+            case 0x44:         /* DRAMaddrHi */
+                GUSregd(GUSDRAMPOS24bit) =
+                    (GUSregd(GUSDRAMPOS24bit) & 0xffff) | ((data & 0x0f) << 16);
+                break;
+            case 0x45:         /* TCtrlReg */
+                GUSregb(GUS45TimerCtrl) = (GUSbyte) data;
+                if (!(data & 0x20))
+                    GUSregb(TimerStatus2x8) &= 0xe7;    /* sb IRQ dis? -> clear 2x8/2xC sb IRQ flags */
+                if (!(data & 0x02))
+                    GUSregb(TimerStatus2x8) &= 0xfe;    /* adlib data IRQ dis? -> clear 2x8 adlib IRQ flag */
+                if (!(GUSregb(TimerStatus2x8) & 0x19))
+                    GUSregb(IRQStatReg2x6) &= 0xef;     /* 0xe6; $$clear IRQ if both IRQ bits are inactive or cleared */
+                /* catch up delayed timer IRQs: */
+                if ((GUSregw(TimerIRQs) > 1) && (GUSregb(TimerDataReg2x9) & 3))
+                {
+                    if (GUSregb(TimerDataReg2x9) & 1)   /* start timer 1 (80us decrement rate) */
+                    {
+                        if (!(GUSregb(TimerDataReg2x9) & 0x40))
+                            GUSregb(TimerStatus2x8) |= 0xc0;    /* maskable bits */
+                        if (data & 4) /* timer1 irq enable */
+                        {
+                            GUSregb(TimerStatus2x8) |= 4;       /* nonmaskable bit */
+                            GUSregb(IRQStatReg2x6) |= 4;        /* timer 1 irq pending */
+                        }
+                    }
+                    if (GUSregb(TimerDataReg2x9) & 2)   /* start timer 2 (320us decrement rate) */
+                    {
+                        if (!(GUSregb(TimerDataReg2x9) & 0x20))
+                            GUSregb(TimerStatus2x8) |= 0xa0;    /* maskable bits */
+                        if (data & 8) /* timer2 irq enable */
+                        {
+                            GUSregb(TimerStatus2x8) |= 2;       /* nonmaskable bit */
+                            GUSregb(IRQStatReg2x6) |= 8;        /* timer 2 irq pending */
+                        }
+                    }
+                    GUSregw(TimerIRQs)--;
+                    if (GUSregw(BusyTimerIRQs) > 1)
+                        GUSregw(BusyTimerIRQs)--;
+                    else
+                        GUSregw(BusyTimerIRQs) =
+                            GUS_irqrequest(state, state->gusirq, GUSregw(TimerIRQs));
+                }
+                else
+                    GUSregw(TimerIRQs) = 0;
+
+                if (!(data & 0x04))
+                {
+                    GUSregb(TimerStatus2x8) &= 0xfb; /* clear non-maskable timer1 bit */
+                    GUSregb(IRQStatReg2x6)  &= 0xfb;
+                }
+                if (!(data & 0x08))
+                {
+                    GUSregb(TimerStatus2x8) &= 0xfd; /* clear non-maskable timer2 bit */
+                    GUSregb(IRQStatReg2x6)  &= 0xf7;
+                }
+                if (!GUSregb(IRQStatReg2x6))
+                    GUS_irqclear(state, state->gusirq);
+                break;
+            case 0x46:          /* Counter1 */
+                GUSregb(GUS46Counter1) = (GUSbyte) data;
+                break;
+            case 0x47:          /* Counter2 */
+                GUSregb(GUS47Counter2) = (GUSbyte) data;
+                break;
+            /* case 0x48:       */ /* sampling freq reg not emulated (same as interwave) */
+            case 0x49:          /* SampCtrlReg */
+                GUSregb(GUS49SampCtrl) = (GUSbyte) data;
+                break;
+            /* case 0x4b:       */ /* joystick trim not emulated */
+            case 0x4c:          /* GUSreset */
+                GUSregb(GUS4cReset) = (GUSbyte) data;
+                if (!(GUSregb(GUS4cReset) & 1)) /* reset... */
+                {
+                    GUSregd(voicewavetableirq) = 0;
+                    GUSregd(voicevolrampirq) = 0;
+                    GUSregw(TimerIRQs) = 0;
+                    GUSregw(BusyTimerIRQs) = 0;
+                    GUSregb(NumVoices) = 0xcd;
+                    GUSregb(IRQStatReg2x6) = 0;
+                    GUSregb(TimerStatus2x8) = 0;
+                    GUSregb(AdLibData2x9) = 0;
+                    GUSregb(TimerDataReg2x9) = 0;
+                    GUSregb(GUS41DMACtrl) = 0;
+                    GUSregb(GUS45TimerCtrl) = 0;
+                    GUSregb(GUS49SampCtrl) = 0;
+                    GUSregb(GUS4cReset) &= 0xf9; /* clear IRQ and DAC enable bits */
+                    GUS_irqclear(state, state->gusirq);
+                }
+                /* IRQ enable bit checked elsewhere */
+                /* EnableDAC bit may be used by external callers */
+                break;
+            }
+        }
+        break;
+    case 0x307:                /* DRAMaccess */
+        {
+            GUSbyte        *adr;
+            adr = state->himemaddr + (GUSregd(GUSDRAMPOS24bit) & 0xfffff);
+            *adr = (GUSbyte) data;
+        }
+        break;
+    }
+}
+
+/* Attention when breaking up a single DMA transfer to multiple ones:
+ * it may lead to multiple terminal count interrupts and broken transfers:
+ *
+ * 1. Whenever you transfer a piece of data, the gusemu callback is invoked
+ * 2. The callback may generate a TC irq (if the register was set up to do so)
+ * 3. The irq may result in the program using the GUS to reprogram the GUS
+ *
+ * Some programs also decide to upload by just checking if TC occurs
+ * (via interrupt or a cleared GUS dma flag)
+ * and then start the next transfer, without checking DMA state
+ *
+ * Thus: Always make sure to set the TC flag correctly!
+ *
+ * Note that the genuine GUS had a granularity of 16 bytes/words for low/high DMA
+ * while later cards had atomic granularity provided by an additional GUS50DMAHigh register
+ * GUSemu also uses this register to support byte-granular transfers for better compatibility
+ * with emulators other than GUSemu32
+ */
+
+void gus_dma_transferdata(GUSEmuState * state, char *dma_addr, unsigned int count, int TC)
+{
+    /* this function gets called by the callback function as soon as a DMA transfer is about to start
+     * dma_addr is a translated address within accessible memory, not the physical one,
+     * count is (real dma count register)+1
+     * note that the amount of bytes transfered is fully determined by values in the DMA registers
+     * do not forget to update DMA states after transferring the entire block:
+     * DREQ cleared & TC asserted after the _whole_ transfer */
+
+    char           *srcaddr;
+    char           *destaddr;
+    char            msbmask = 0;
+    GUSbyte        *gusptr;
+    gusptr = state->gusdatapos;
+
+    srcaddr = dma_addr; /* system memory address */
+    {
+        int             offset = (GUSregw(GUS42DMAStart) << 4) + (GUSregb(GUS50DMAHigh) & 0xf);
+        if (state->gusdma >= 4)
+            offset = (offset & 0xc0000) + (2 * (offset & 0x1fff0)); /* 16 bit address translation */
+        destaddr = (char *) state->himemaddr + offset; /* wavetable RAM adress */
+    }
+
+    GUSregw(GUS42DMAStart) += (GUSword)  (count >> 4);                           /* ToDo: add 16bit GUS page limit? */
+    GUSregb(GUS50DMAHigh)   = (GUSbyte) ((count + GUSregb(GUS50DMAHigh)) & 0xf); /* ToDo: add 16bit GUS page limit? */
+
+    if (GUSregb(GUS41DMACtrl) & 0x02)   /* direction, 0 := sysram->gusram */
+    {
+        char           *tmpaddr = destaddr;
+        destaddr = srcaddr;
+        srcaddr = tmpaddr;
+    }
+
+    if ((GUSregb(GUS41DMACtrl) & 0x80) && (!(GUSregb(GUS41DMACtrl) & 0x02)))
+        msbmask = (const char) 0x80;    /* invert MSB */
+    for (; count > 0; count--)
+    {
+        if (GUSregb(GUS41DMACtrl) & 0x40)
+            *(destaddr++) = *(srcaddr++);               /* 16 bit lobyte */
+        else
+            *(destaddr++) = (msbmask ^ (*(srcaddr++))); /* 8 bit */
+        if (state->gusdma >= 4)
+            *(destaddr++) = (msbmask ^ (*(srcaddr++))); /* 16 bit hibyte */
+    }
+
+    if (TC)
+    {
+        (GUSregb(GUS41DMACtrl)) &= 0xfe;        /* clear DMA request bit */
+        if (GUSregb(GUS41DMACtrl) & 0x20)       /* DMA terminal count IRQ */
+        {
+            GUSregb(IRQStatReg2x6) |= 0x80;
+            GUS_irqrequest(state, state->gusirq, 1);
+        }
+    }
+}