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   1 /****************************************************************************
   2  *                                                          __              *
   3  *                ____ ___  ____ __  ______ ___  ____  ____/ /              *
   4  *               / __ `__ \/ __ `/ |/ / __ `__ \/ __ \/ __  /               *
   5  *              / / / / / / /_/ />  </ / / / / / /_/ / /_/ /                *
   6  *             /_/ /_/ /_/\__,_/_/|_/_/ /_/ /_/\____/\__,_/                 *
   7  *                                                                          *
   8  *                    Module Processing (ARM segment)                       *
   9  *                                                                          *
  10  *         Copyright (c) 2008, Mukunda Johnson (mukunda@maxmod.org)         *
  11  *                                                                          *
  12  * Permission to use, copy, modify, and/or distribute this software for any *
  13  * purpose with or without fee is hereby granted, provided that the above   *
  14  * copyright notice and this permission notice appear in all copies.        *
  15  *                                                                          *
  16  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES *
  17  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF         *
  18  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR  *
  19  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES   *
  20  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN    *
  21  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF  *
  22  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.           *
  23  ****************************************************************************/
  24
  25 @=============================================================
  26 @                         DEFINITIONS
  27 @=============================================================
  28
  29 #include "mp_format_mas.inc"
  30 #include "mp_mas_structs.inc"
  31 #include "mp_defs.inc"
  32 #include "mp_macros.inc"
  33
  34 #ifdef SYS_GBA
  35 #include "mp_mixer_gba.inc"
  36 #include "swi_gba.inc"
  37 #endif
  38
  39 #ifdef SYS_NDS
  40 #include "mp_mixer_ds.inc"
  41 #include "swi_nds.inc"
  42 #endif
  43
  44 __SECTION_IWRAM
  45
  46 .arm
  47 .align 2
  48
  49 .global mmAllocChannel
  50 @********************************************************
  51 mmAllocChannel:
  52 @********************************************************
  53 // finds a channel to use
  54 // returns invalid channel [255] if none available
  55         push    {r4,r5,r6}                              // preserve regs
  56         ldr     r5,=mm_ch_mask                  // read channel mask
  57         ldr     r5, [r5]
  58         ldr     r1,=mm_achannels                // pointer to active channels
  59         ldr     r1, [r1]
  60         add     r1, #MCA_FVOL
  61         mov     r0, #0                          // r0 = counter
  62         mov     r2, #0x80000000                 // r2 = min vol
  63         mov     r3, #255                        // r3 = best channel [255=none]
  64         mov     r6, #ACHN_BACKGROUND
  65         b       .mppac_start
  66 .mppac_skip:
  67         add     r1, #MCA_SIZE
  68 .mppac_next_test:
  69         cmp     r5, #0
  70 .mppac_next_notest:
  71         beq     .mppac_finished
  72         add     r0, #1
  73 .mppac_start:
  74         movs    r5, r5, lsr#1                   // 1    shift out channel bit
  75         bcc     .mppac_skip                     // 1/3  skip if cleared
  76         ldrh    r4, [r1], #MCA_SIZE             // 5    read type setting & increment pointer
  77         cmp     r6, r4, lsr #8                  // 1    compare background/disabled
  78         blt     .mppac_next_test                // 1/3  if > background then its important, dont use this channel
  79         bgt     .mppac_found                    // 1/3  if < background then its disabled, use this channel
  80
  81         cmp     r2, r4, lsl#23                  // 1    compare volume with our record
  82         bls     .mppac_next_test                // 1/3  goto next if not less
  83         mov     r3, r0                          // 1    otherwise save this channel
  84         movs    r2, r4, lsl#23                  // 1    and volume level
  85 //      beq     .mppac_finished                 // 1/3  exit immediately if volume is zero
  86         b       .mppac_next_test                // 3    loop
  87                                                 // 17
  88 .mppac_finished:
  89         mov     r0, r3
  90 //      cmp     r0, #255        //trap
  91 //      5: bge 5b
  92 .mppac_found:
  93         pop     {r4,r5,r6}
  94         bx      lr
  95
  96 .global mmReadPattern
  97 @****************************************************
  98 mmReadPattern:
  99 @****************************************************
 100         push    {r10-r12}
 101         ldr     r11, [r8, #MPL_SONGADR]
 102         ldrb    r12, [r11, #C_MAS_INSTN]        // read instr count
 103         ldrb    r11, [r8, #MPL_FLAGS]           // read flags
 104         mov     r10, #1                         // for various things
 105
 106         ldr     r0,=mpp_channels
 107         ldr     r9, [r0]
 108         ldr     r7, [r8, #MPL_PATTREAD]
 109         ldr     r0,=mpp_vars
 110         str     r7, [r0, #MPV_PATTREAD_P]
 111
 112         mov     r1, #0
 113
 114 @----------------------------------------------------------------
 115 readpattern:
 116 @----------------------------------------------------------------
 117
 118         mov     r5, #0                  // clear flags
 119         ldrb    r3, [r7], #1            // read pattern byte
 120         movs    r3, r3, lsl#32-7        // mask channel#
 121         beq     end_of_row              // 0 = end of row
 122         rsb     r3, r10, r3, lsr#32-7   // get channel number
 123         orr     r1, r10, lsl r3
 124         mov     r0, #MCH_SIZE
 125         mla     r6, r3, r0, r9          // get channel pointer
 126         ldrcsb  r2, [r7], #1            // read new maskvariable if bit was set
 127         strcsb  r2, [r6, #MCH_CFLAGS]   // and save it
 128         ldrccb  r2, [r6, #MCH_CFLAGS]   // otherwise read previous flags
 129
 130         tst     r2, #1                  // test note bit
 131         beq     no_note
 132         ldrb    r0, [r7], #1            // read note value
 133         cmp     r0, #254                // test if < 254
 134         strltb  r0, [r6, #MCH_PNOTE]    // [most common result]
 135         blt     no_note
 136         orreq   r5, #MF_NOTECUT         // 254 is note-cut
 137         orrgt   r5, #MF_NOTEOFF         // 255 is note-off
 138 no_note:
 139
 140         tst     r2, #2                  // shift out instrument bit
 141         beq     no_instrument
 142         ldrb    r0, [r7], #1            // read instrument value
 143         tst     r5, #MF_NOTEOFF|MF_NOTECUT
 144         bne     no_instrument           // skip if note-off or cut is set
 145         cmp     r0, r12                 // check if value > max instruments
 146         movgt   r0, #0                  // zero if so
 147         ldrb    r3, [r6, #MCH_INST]     // test if instrument is the same
 148         cmp     r0, r3
 149         beq     same_instrument
 150         movs    r3, r11, lsr#C_FLAGS_LS // shift out 'mod/s3m' flag
 151         orrcs   r5, #MF_START           // set start flag if old
 152         orr     r5, #MF_NEWINSTR        // set new instrument flag
 153 same_instrument:
 154         strb    r0, [r6, #MCH_INST]
 155 no_instrument:
 156
 157         tst     r10, r2, lsr#3          // test volume & effect bits
 158         ldrcsb  r0, [r7], #1            // copy vcmd
 159         strcsb  r0, [r6, #MCH_VOLCMD]
 160 no_vcmd:
 161         beq     no_effect
 162         ldrb    r0, [r7], #1            // copy effect
 163         ldrb    r3, [r7], #1            // copy param
 164         orr     r0, r3, lsl#8
 165         strh    r0, [r6, #MCH_EFFECT]   // write effect+param
 166 no_effect:
 167         orr     r5, r2, lsr#4           // orr in the new flags
 168         strb    r5, [r6, #MCH_FLAGS]    // save flags
 169         b       readpattern             // loop
 170 end_of_row:
 171         str     r7, [r8, #MPL_PATTREAD] // save read position
 172         str     r1, [r8, #MPL_MCH_UPDATE] // save update bits
 173         pop     {r10-r12}
 174         bx      lr                      // return
 175
 176 .macro get_channel branch
 177         ldrb    r0, [r7, #MCH_ALLOC]    // get channel
 178         cmp     r0, #255                //
 179         bge     \branch         // no channel!
 180         ldr     r6,=mm_achannels        //
 181         ldr     r6, [r6]                //
 182         mov     r1, #MCA_SIZE           //
 183         mla     r6, r0, r1, r6          //
 184 .endm
 185
 186 .global mmUpdateChannel_T0, mmUpdateChannel_TN
 187 @***************************************************************************
 188 mmUpdateChannel_T0:                     // for tick 0
 189 @***************************************************************************
 190         push    {lr}
 191
 192         ldrb    r5, [r7, #MCH_FLAGS]    // read channel flags
 193         tst     r5, #MF_START           // test start flag
 194         beq     dont_start_channel      // skip section if cleared
 195
 196         tst     r5, #MF_HASFX           // test effect flag
 197         beq     no_channel_effect
 198         ldrh    r0, [r7, #MCH_EFFECT]   // read effect
 199         and     r1, r0, #0xFF
 200 //      cmp     r1, #19                 // test for 'SDx' (note delay)
 201 //      lsreq   r2, r0, #12
 202 //      cmpeq   r2, #0xD
 203 //      beq     dont_start_channel      // dont start channel if delayed
 204
 205                                         // test for glissando
 206         tst     r5, #MF_NEWINSTR
 207         bne     start_channel           // always start channel if it's a new instrument
 208         cmp     r1, #0x7                // test if effect is Gxx
 209         beq     glissando_affected
 210
 211 no_channel_effect:
 212         tst     r5, #MF_NEWINSTR        // copeee
 213         bne     start_channel           // always start channel if it's a new instrument
 214
 215         tst     r5, #MF_HASVCMD         // test for volume commmand
 216         beq     start_channel           // none = start channel
 217         ldrb    r0, [r8, #MPL_FLAGS]    // read mod flags
 218         movs    r0, r0, lsr#C_FLAGS_XS  // test for XM mode
 219         ldrb    r0, [r7, #MCH_VOLCMD]   // read volume command
 220         bcs     xm_vcmd                 // branch
 221 it_vcmd:                                // using IT effects:
 222         cmp     r0, #193                // glissando is 193..202
 223         blt     start_channel
 224         cmp     r0, #202
 225         bgt     start_channel
 226         b       glissando_affected
 227 xm_vcmd:                                // using XM effects:
 228         cmp     r0, #0xF0               // glissando is Fx
 229         bge     glissando_affected
 230         b       start_channel
 231 no_channel_vcmd:
 232
 233 glissando_affected:
 234
 235         get_channel start_channel
 236 /*      ldrb    r0, [r7, #MCH_ALLOC]    // if channel is invalid
 237         cmp     r0, #255                // then skip this
 238         bge     start_channel
 239
 240         ldr     r6,=mm_achannels        // get channel
 241         ldr     r6, [r6]                //
 242         mov     r1, #MCA_SIZE           //
 243         mla     r6, r0, r1, r6          //
 244 */
 245         bl      mmChannelStartACHN      // start achn
 246         bic     r5, #MF_START           // clear start flag
 247         strb    r5, [r7, #MCH_FLAGS]
 248         b       dont_start_channel
 249
 250 start_channel:                          // ok start channel...
 251
 252         ldr     r2,=mpp_Channel_NewNote
 253         mov     lr, pc
 254         bx      r2
 255         get_channel     mmUpdateChannel_TN_
 256
 257 //      cmp     r6, #0
 258 //      beq     mmUpdateChannel_TN_
 259
 260         bl      mmChannelStartACHN      // start achn
 261 //----------------------------------------------
 262         // r2 = note, calculate period
 263         ldrb    r0, [r6, #MCA_SAMPLE]
 264         subs    r0, #1
 265         bcc     no_sample_to_make_period
 266
 267         ldrb    r1, [r8, #MPL_FLAGS]
 268         lsrs    r1, #C_FLAGS_SS
 269         bcs     linear_periods
 270
 271         ldr     r3, [r8, #MPL_SONGADR]  // read song addr
 272         ldr     r1, [r8, #MPL_SAMPTABLE]// get sample table
 273         ldr     r0, [r1, r0, lsl#2]     // get sample address
 274         add     r0, r3                  // add module base
 275
 276         ldrh    r1, [r0, #C_MASS_FREQ]  // read tuning freq
 277         lsl     r1, #2                  // shift ...
 278 //      mov     r0, r2                  // move this.
 279         bl      get_amiga_period
 280         b       got_period
 281 linear_periods:
 282         LDR     R1,=IT_PitchTable
 283         LDR     R0, [R1, R2, LSL#2]
 284         //bl    get_linear_period
 285 got_period:
 286 //--------------------------------
 287
 288 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
 289         str     r0, [r7, #MCH_PERIOD]   // save period
 290         ldrb    r0, [r6, #MCA_FLAGS]    // set start flag
 291         orr     r0, #MCAF_START
 292         strb    r0, [r6, #MCA_FLAGS]
 293 no_sample_to_make_period:
 294 //----------------------------------------------------
 295
 296         b       channel_started
 297
 298 dont_start_channel:
 299
 300         get_channel     mmUpdateChannel_TN___
 301
 302 channel_started:
 303         tst     r5, #MF_DVOL
 304         beq     dvol_skip
 305         ldrb    r0, [r7, #MCH_INST]
 306         subs    r0, #1
 307         bcc     dvol_no_instrument
 308
 309         ldr     r2, [r8, #MPL_SONGADR]  // get instrument pointer
 310         ldr     r1, [r8, #MPL_INSTTABLE]
 311         ldr     r0, [r1, r0, lsl#2]
 312         add     r0, r2
 313
 314         ldr     r1, [r0, #C_MASI_NNA]   // read nna,envflags,pan
 315         ldrb    r2, [r7, #MCH_BFLAGS]   // read bflags
 316         bic     r2, #0b11000000         // clear old nna
 317         orr     r2, r1, lsl#6           // set new nna
 318         strb    r2, [r7, #MCH_BFLAGS]
 319
 320         ldrb    r2, [r6, #MCA_FLAGS]    // read achn flags
 321         bic     r2, #MCAF_VOLENV
 322         tst     r1, #ENVFLAG_A<<8
 323         orrne   r2, #MCAF_VOLENV
 324         strb    r2, [r6, #MCA_FLAGS]
 325
 326         movs    r1, r1, lsl#8+1         // shift out panning MSB
 327         movcs   r1, r1, lsr#24          // if set, use new panning value
 328         strcsb  r1, [r7, #MCH_PANNING]
 329 dvol_no_instrument:
 330
 331         ldrb    r0, [r6, #MCA_SAMPLE]   // read sample#
 332         subs    r0, #1
 333         bcc     dvol_no_sample          // exit if invalid
 334
 335         ldr     r2, [r8, #MPL_SONGADR]  // get sample address
 336         ldr     r1, [r8, #MPL_SAMPTABLE]
 337         ldr     r0, [r1, r0, lsl#2]
 338         //add   r0, r2
 339
 340         ldrh    r1, [r0, r2]
 341         //ldrh  r1, [r0, #C_MASS_DV]    // read dvol & pan
 342         strb    r1, [r7, #MCH_VOLUME]   // copy volume
 343         movs    r1, r1, lsl#24-7
 344         mov     r1, r1, lsr#24
 345         strcsb  r1, [r7, #MCH_PANNING]
 346 dvol_skip:
 347 dvol_no_sample:
 348
 349         tst     r5, #MF_START|MF_DVOL
 350         beq     dont_reset_volume
 351
 352         ldrb    r0, [r8, #MPL_FLAGS]
 353         tst     r0, #C_FLAGS_X
 354         beq     1f
 355         tst     r5, #MF_DVOL
 356         beq     dont_reset_volume       // xm stuff
 357 1:
 358 reset_volume:
 359         mov     r0, #(1<<10)            // [1]
 360         mov     r1, #0                  // [1]
 361         mov     r2, #0                  // [1]
 362         add     r12, r6, #MCA_FADE      // [1]
 363         stmia   r12, {r0-r2}            // [19]
 364                                         // [23]
 365         strh    r1, [r6, #MCA_ENVN_VOL]
 366         strb    r1, [r6, #MCA_ENVN_PIC]
 367
 368         // the last bit of code sets fade to (1<<10)
 369         // and clears ENVC_VOL,ENVC_PAN,ENVC_PIC,
 370         // AVIB_DEP, and AVIB_POS
 371         // second bit clears ENVN vars
 372
 373         strb    r1, [r7, #MCH_FXMEM]    // clear fx memory
 374
 375         ldrb    r1, [r6, #MCA_FLAGS]    // set keyon
 376         orr     r1, #MCAF_KEYON         // and clear envend+fade
 377         bic     r1, #MCAF_ENVEND | MCAF_FADE
 378         strb    r1, [r6, #MCA_FLAGS]
 379
 380 dont_reset_volume:
 381
 382         tst     r5, #MF_NOTEOFF         // test noteoff bit
 383         beq     skip_noteoff
 384
 385         ldrb    r1, [r6, #MCA_FLAGS]    // read flags
 386         bic     r1, #MCAF_KEYON         // clear key-on
 387         ldrb    r0, [r8, #MPL_FLAGS]    // read mod flags
 388         tst     r0, #C_FLAGS_X          // test xm mode
 389         orrne   r1, #MCAF_FADE          // XM starts fade immediately on note-off
 390         strb    r1, [r6, #MCA_FLAGS]
 391 skip_noteoff:
 392
 393         tst     r5, #MF_NOTECUT         // test notecut bit
 394         movne   r0, #0                  // clear volume
 395         strneb  r0, [r7, #MCH_VOLUME]   // on note-cut
 396
 397         bic     r5, #MF_START           // clear start flag
 398         strb    r5, [r7, #MCH_FLAGS]    // save flags
 399         b       mmUpdateChannel_TN_
 400 @************************************************************
 401 mmUpdateChannel_TN:                     // for other ticks
 402 @************************************************************
 403         push    {lr}
 404
 405 mmUpdateChannel_TN_:
 406         ldrb    r0, [r7, #MCH_ALLOC]    // get channel
 407         cmp     r0, #255                //
 408         bge     mmUpdateChannel_TN___   // no channel!
 409         ldr     r6,=mm_achannels        //
 410         ldr     r6, [r6]                //
 411         mov     r1, #MCA_SIZE           //
 412         mla     r6, r0, r1, r6          //
 413
 414 mmUpdateChannel_TN___:
 415
 416         movge   r6, #0
 417
 418         ldr     r5, [r7, #MCH_PERIOD]           // r5 will be used to hold the period
 419         ldr     r1,=mpp_vars
 420         mov     r0, #0
 421         strb    r0, [r1, #MPV_SAMPOFF]          // clear variables
 422         strb    r0, [r1, #MPV_VOLPLUS]
 423         strb    r0, [r1, #MPV_PANPLUS]
 424         strb    r0, [r1, #MPV_NOTEDELAY]
 425
 426 //---------------------------------------------
 427 // Update Volume Commands
 428 //---------------------------------------------
 429
 430         ldrb    r0, [r7, #MCH_FLAGS]
 431         tst     r0, #MF_HASVCMD
 432         ldrne   r1,=mpp_Process_VolumeCommand
 433         movne   lr, pc
 434         bxne    r1
 435         //blne  mpp_Process_VolumeCommand
 436
 437 //---------------------------------------------
 438 // Update Effects
 439 //---------------------------------------------
 440
 441         ldrb    r0, [r7, #MCH_FLAGS]
 442         tst     r0, #MF_HASFX
 443         ldrne   r1,=mpp_Process_Effect
 444         movne   lr, pc
 445         bxne    r1
 446         //blne  mpp_Process_Effect
 447
 448 //---------------------------------------------
 449
 450         cmp     r6, #0
 451         beq     no_achn
 452         ldrh    r0, [r7, #MCH_VOLUME]   // read volume & cvolume
 453         and     r1, r0, #255            // mask volume
 454         mov     r0, r0, lsr#8           // mask cvolume
 455         mul     r0, r1, r0              // multiply together
 456         mov     r0, r0, lsr#5           // shift
 457         strb    r0, [r6, #MCA_VOLUME]   // save in achn volume
 458
 459         ldr     r1,=mpp_vars            //
 460         ldrsb   r2, [r1, #MPV_VOLPLUS]  // read volume addition
 461         adds    r0, r2, lsl#3           // add to volume
 462         movmi   r0, #0
 463         cmp     r0, #129
 464         movcs   r0, #128
 465         strb    r0, [r1, #MPV_AFVOL]    // store in immediate vol
 466
 467         ldrb    r0, [r1, #MPV_NOTEDELAY]// read note delay
 468         cmp     r0, #0                  // dont update if nonzero
 469         beq     channel_update_achn
 470
 471         ldrb    r0, [r6, #MCA_FLAGS]
 472         orr     r0, #MCAF_UPDATED
 473         strb    r0, [r6, #MCA_FLAGS]
 474         b       no_achn
 475
 476 channel_update_achn:
 477
 478         ldrb    r0, [r7, #MCH_PANNING]  // copy panning
 479         strb    r0, [r6, #MCA_PANNING]
 480         ldr     r0, [r7, #MCH_PERIOD]   // copy period
 481         str     r0, [r6, #MCA_PERIOD]
 482         mov     r0, #0
 483         strh    r0, [r1, #MPV_PANPLUS]  // WHAT IS THIS??? "@ <---- RESERVED FOR LATER USE, CLEAR TO ZERO TEMPORARILY"
 484
 485         ldrb    r0, [r6, #MCA_FLAGS]
 486         orr     r0, #MCAF_UPDATED
 487         strb    r0, [r6, #MCA_FLAGS]
 488
 489         push    {r4}
 490         ldrb    r4, [r7, #MCH_ALLOC]
 491         ldr     r1,=mpp_Update_ACHN_notest
 492         mov     lr, pc
 493         bx      r1
 494
 495         pop     {r4}
 496 no_achn:
 497         pop     {lr}
 498         bx      lr
 499
 500 @***********************************************************
 501 mmChannelStartACHN:             // returns r2=note
 502 @***********************************************************
 503         ldrb    r2, [r7, #MCH_BFLAGS+1]         // clear tremor/cutvol
 504         bic     r2, #0b110
 505         strb    r2, [r7, #MCH_BFLAGS+1]
 506
 507         cmp     r6, #0                          // achn==0?
 508         beq     1f                              // then skip this part
 509
 510         mov     r0, #ACHN_FOREGROUND            // set foreground type
 511         strb    r0, [r6, #MCA_TYPE]
 512
 513         ldrb    r0, [r6, #MCA_FLAGS]            // read flags
 514         bic     r0, #0b11000000                 // clear SUB, EFFECT
 515         ldr     r1,=mpp_clayer                  // get layer
 516         ldrb    r1, [r1]
 517         orr     r0, r1, lsl#6                   // orr into flags
 518         orr     r0, r10, r0, lsl#8              // orr PARENT
 519         strh    r0, [r6, #MCA_PARENT]           // store parent/flags
 520         ldrb    r0, [r7, #MCH_INST]             // copy instrument
 521         strb    r0, [r6, #MCA_INST]
 522 1:      ldreqb  r0, [r7, #MCH_INST]
 523         subs    r0, #1
 524         bcc     invalid_instrument
 525
 526         ldr     r2, [r8, #MPL_SONGADR]          // get instrument pointer
 527         ldr     r1, [r8, #MPL_INSTTABLE]
 528         ldr     r0, [r1, r0, lsl#2]
 529         add     r0, r2
 530
 531         ldrb    r2, [r7, #MCH_PNOTE]            // get pattern note
 532
 533         ldrh    r1, [r0, #C_MASI_MAP]           // read notemap offset
 534         tst     r1, #0x8000                     // test MSB
 535         beq     full_notemap                    // if set: notemap doesnt exist!
 536                                                 // use single entry
 537         cmp     r6, #0                          // if channel is valid
 538         strneb  r1, [r6, #MCA_SAMPLE]           //   write sample value
 539         strb    r2, [r7, #MCH_NOTE]             // write note value (without notemap, all entries == PNOTE)
 540         bx      lr                              // return
 541
 542 full_notemap:
 543
 544         add     r0, r2, lsl#1                   // add note offset
 545         ldrh    r2, [r0, r1]                    // read notemap entry [instr+note*2+notemap_offset]
 546         strb    r2, [r7, #MCH_NOTE]             // write note value
 547         cmp     r6, #0                          // if channel is valid
 548         mov     r0, r2, lsr#8                   //   write sample value
 549         strneb  r0, [r6, #MCA_SAMPLE]           //   ..
 550         and     r2, #255
 551 invalid_instrument:
 552         bx      lr                              // return
 553
 554 /**********
 555
 556         cmp     r6, #0                          // read notemap [sample]
 557         ldrneb  r2, [r0, #C_MASI_MAP+1]
 558         strneb  r2, [r6, #MCA_SAMPLE]
 559
 560 //invalid_instrument:                           // BUG???
 561         ldrb    r2, [r0, #C_MASI_MAP]           // read notemap [note]
 562         strb    r2, [r7, #MCH_NOTE]
 563 invalid_instrument:
 564
 565         bx      lr
 566 **************/
 567
 568 .global mmGetPeriod
 569 @***********************************************************
 570 mmGetPeriod:
 571 @***********************************************************
 572
 573         ldrb    r0, [r8, #MPL_FLAGS]
 574         lsrs    r0, #C_FLAGS_SS
 575         bcs     get_linear_period       // tuning not used here with linear periods
 576
 577 get_amiga_period:
 578         adr     r3, note_table_mod      // get octave/mod from note
 579         ldrb    r0, [r3, r2]
 580         sub     r3, #3*10
 581         ldrb    r2, [r3, r2, lsr#2]
 582
 583         // r0 = (note mod 12) << 1
 584         // r1 = tuning
 585         // r2 = (note / 12)
 586
 587         ldr     r3,=ST3_FREQTABLE       // read st3 table entry
 588         ldrh    r0, [r3, r0]
 589
 590         mov     r3, #0x00AB0            // r3 = 133808
 591         orr     r3, #0x20000
 592         mul     r0, r3, r0              // multiply by magic number...
 593         mov     r0, r0, lsr r2          // shift by octave
 594         cmp     r1, #0
 595         beq     1f
 596         swi     SWI_DIVIDE<<16          // divide value / tuning
 597 1:      bx      lr
 598
 599 .global note_table_oct  // remove this, make this static
 600 .global note_table_mod  // remove this, make this staic
 601 note_table_oct:
 602 .byte   0,0,0,1,1,1,2,2,2,3,3,3,4,4,4,5,5,5, 6,6,6 ,7,7,7,8,8,8,9,9,9
 603 note_table_mod:
 604 .byte   0,2,4,6,8,10,12,14,16,18,20,22,0,2,4,6,8,10,12,14,16,18,20,22,0,2,4,6,8,10,12,14,16,18,20,22,0,2,4,6,8,10,12,14,16,18,20,22,0,2,4,6,8,10,12,14,16,18,20,22,0,2,4,6,8,10,12,14,16,18,20,22,0,2,4,6,8,10,12,14,16,18,20,22,0,2,4,6,8,10,12,14,16,18,20,22,0,2,4,6,8,10,12,14,16,18,20,22,0
 605 .align 2
 606
 607 get_linear_period:
 608         ldr     r1,=IT_PitchTable
 609         ldr     r0, [r1, r2, lsl#2]
 610         bx      lr
 611
 612 .pool