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   1 /* Name: usbdrvasm165.inc
   2  * Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers
   3  * Author: Christian Starkjohann
   4  * Creation Date: 2007-04-22
   5  * Tabsize: 4
   6  * Copyright: (c) 2007 by OBJECTIVE DEVELOPMENT Software GmbH
   7  * License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt)
   8  * Revision: $Id: usbdrvasm165.inc 740 2009-04-13 18:23:31Z cs $
   9  */
  10
  11 /* Do not link this file! Link usbdrvasm.S instead, which includes the
  12  * appropriate implementation!
  13  */
  14
  15 /*
  16 General Description:
  17 This file is the 16.5 MHz version of the USB driver. It is intended for the
  18 ATTiny45 and similar controllers running on 16.5 MHz internal RC oscillator.
  19 This version contains a phase locked loop in the receiver routine to cope with
  20 slight clock rate deviations of up to +/- 1%.
  21
  22 See usbdrv.h for a description of the entire driver.
  23
  24 Since almost all of this code is timing critical, don't change unless you
  25 really know what you are doing! Many parts require not only a maximum number
  26 of CPU cycles, but even an exact number of cycles!
  27 */
  28
  29 ;Software-receiver engine. Strict timing! Don't change unless you can preserve timing!
  30 ;interrupt response time: 4 cycles + insn running = 7 max if interrupts always enabled
  31 ;max allowable interrupt latency: 59 cycles -> max 52 cycles interrupt disable
  32 ;max stack usage: [ret(2), r0, SREG, YL, YH, shift, x1, x2, x3, x4, cnt] = 12 bytes
  33 ;nominal frequency: 16.5 MHz -> 11 cycles per bit
  34 ; 16.3125 MHz < F_CPU < 16.6875 MHz (+/- 1.1%)
  35 ; Numbers in brackets are clocks counted from center of last sync bit
  36 ; when instruction starts
  37
  38
  39 USB_INTR_VECTOR:
  40 ;order of registers pushed: YL, SREG [sofError], r0, YH, shift, x1, x2, x3, x4, cnt
  41     push    YL                  ;[-23] push only what is necessary to sync with edge ASAP
  42     in      YL, SREG            ;[-21]
  43     push    YL                  ;[-20]
  44 ;----------------------------------------------------------------------------
  45 ; Synchronize with sync pattern:
  46 ;----------------------------------------------------------------------------
  47 ;sync byte (D-) pattern LSb to MSb: 01010100 [1 = idle = J, 0 = K]
  48 ;sync up with J to K edge during sync pattern -- use fastest possible loops
  49 ;The first part waits at most 1 bit long since we must be in sync pattern.
  50 ;YL is guarenteed to be < 0x80 because I flag is clear. When we jump to
  51 ;waitForJ, ensure that this prerequisite is met.
  52 waitForJ:
  53     inc     YL
  54     sbis    USBIN, USBMINUS
  55     brne    waitForJ        ; just make sure we have ANY timeout
  56 waitForK:
  57 ;The following code results in a sampling window of < 1/4 bit which meets the spec.
  58     sbis    USBIN, USBMINUS     ;[-15]
  59     rjmp    foundK              ;[-14]
  60     sbis    USBIN, USBMINUS
  61     rjmp    foundK
  62     sbis    USBIN, USBMINUS
  63     rjmp    foundK
  64     sbis    USBIN, USBMINUS
  65     rjmp    foundK
  66     sbis    USBIN, USBMINUS
  67     rjmp    foundK
  68     sbis    USBIN, USBMINUS
  69     rjmp    foundK
  70 #if USB_COUNT_SOF
  71     lds     YL, usbSofCount
  72     inc     YL
  73     sts     usbSofCount, YL
  74 #endif  /* USB_COUNT_SOF */
  75 #ifdef USB_SOF_HOOK
  76     USB_SOF_HOOK
  77 #endif
  78     rjmp    sofError
  79 foundK:                         ;[-12]
  80 ;{3, 5} after falling D- edge, average delay: 4 cycles [we want 5 for center sampling]
  81 ;we have 1 bit time for setup purposes, then sample again. Numbers in brackets
  82 ;are cycles from center of first sync (double K) bit after the instruction
  83     push    r0                  ;[-12]
  84 ;   [---]                       ;[-11]
  85     push    YH                  ;[-10]
  86 ;   [---]                       ;[-9]
  87     lds     YL, usbInputBufOffset;[-8]
  88 ;   [---]                       ;[-7]
  89     clr     YH                  ;[-6]
  90     subi    YL, lo8(-(usbRxBuf));[-5] [rx loop init]
  91     sbci    YH, hi8(-(usbRxBuf));[-4] [rx loop init]
  92     mov     r0, x2              ;[-3] [rx loop init]
  93     sbis    USBIN, USBMINUS     ;[-2] we want two bits K (sample 2 cycles too early)
  94     rjmp    haveTwoBitsK        ;[-1]
  95     pop     YH                  ;[0] undo the pushes from before
  96     pop     r0                  ;[2]
  97     rjmp    waitForK            ;[4] this was not the end of sync, retry
  98 ; The entire loop from waitForK until rjmp waitForK above must not exceed two
  99 ; bit times (= 22 cycles).
 100
 101 ;----------------------------------------------------------------------------
 102 ; push more registers and initialize values while we sample the first bits:
 103 ;----------------------------------------------------------------------------
 104 haveTwoBitsK:               ;[1]
 105     push    shift           ;[1]
 106     push    x1              ;[3]
 107     push    x2              ;[5]
 108     push    x3              ;[7]
 109     ldi     shift, 0xff     ;[9] [rx loop init]
 110     ori     x3, 0xff        ;[10] [rx loop init] == ser x3, clear zero flag
 111
 112     in      x1, USBIN       ;[11] <-- sample bit 0
 113     bst     x1, USBMINUS    ;[12]
 114     bld     shift, 0        ;[13]
 115     push    x4              ;[14] == phase
 116 ;   [---]                   ;[15]
 117     push    cnt             ;[16]
 118 ;   [---]                   ;[17]
 119     ldi     phase, 0        ;[18] [rx loop init]
 120     ldi     cnt, USB_BUFSIZE;[19] [rx loop init]
 121     rjmp    rxbit1          ;[20]
 122 ;   [---]                   ;[21]
 123
 124 ;----------------------------------------------------------------------------
 125 ; Receiver loop (numbers in brackets are cycles within byte after instr)
 126 ;----------------------------------------------------------------------------
 127 /*
 128 byte oriented operations done during loop:
 129 bit 0: store data
 130 bit 1: SE0 check
 131 bit 2: overflow check
 132 bit 3: catch up
 133 bit 4: rjmp to achieve conditional jump range
 134 bit 5: PLL
 135 bit 6: catch up
 136 bit 7: jump, fixup bitstuff
 137 ; 87 [+ 2] cycles
 138 ------------------------------------------------------------------
 139 */
 140 continueWithBit5:
 141     in      x2, USBIN       ;[055] <-- bit 5
 142     eor     r0, x2          ;[056]
 143     or      phase, r0       ;[057]
 144     sbrc    phase, USBMINUS ;[058]
 145     lpm                     ;[059] optional nop3; modifies r0
 146     in      phase, USBIN    ;[060] <-- phase
 147     eor     x1, x2          ;[061]
 148     bst     x1, USBMINUS    ;[062]
 149     bld     shift, 5        ;[063]
 150     andi    shift, 0x3f     ;[064]
 151     in      x1, USBIN       ;[065] <-- bit 6
 152     breq    unstuff5        ;[066] *** unstuff escape
 153     eor     phase, x1       ;[067]
 154     eor     x2, x1          ;[068]
 155     bst     x2, USBMINUS    ;[069]
 156     bld     shift, 6        ;[070]
 157 didUnstuff6:                ;[   ]
 158     in      r0, USBIN       ;[071] <-- phase
 159     cpi     shift, 0x02     ;[072]
 160     brlo    unstuff6        ;[073] *** unstuff escape
 161 didUnstuff5:                ;[   ]
 162     nop2                    ;[074]
 163 ;   [---]                   ;[075]
 164     in      x2, USBIN       ;[076] <-- bit 7
 165     eor     x1, x2          ;[077]
 166     bst     x1, USBMINUS    ;[078]
 167     bld     shift, 7        ;[079]
 168 didUnstuff7:                ;[   ]
 169     eor     r0, x2          ;[080]
 170     or      phase, r0       ;[081]
 171     in      r0, USBIN       ;[082] <-- phase
 172     cpi     shift, 0x04     ;[083]
 173     brsh    rxLoop          ;[084]
 174 ;   [---]                   ;[085]
 175 unstuff7:                   ;[   ]
 176     andi    x3, ~0x80       ;[085]
 177     ori     shift, 0x80     ;[086]
 178     in      x2, USBIN       ;[087] <-- sample stuffed bit 7
 179     nop                     ;[088]
 180     rjmp    didUnstuff7     ;[089]
 181 ;   [---]                   ;[090]
 182                             ;[080]
 183
 184 unstuff5:                   ;[067]
 185     eor     phase, x1       ;[068]
 186     andi    x3, ~0x20       ;[069]
 187     ori     shift, 0x20     ;[070]
 188     in      r0, USBIN       ;[071] <-- phase
 189     mov     x2, x1          ;[072]
 190     nop                     ;[073]
 191     nop2                    ;[074]
 192 ;   [---]                   ;[075]
 193     in      x1, USBIN       ;[076] <-- bit 6
 194     eor     r0, x1          ;[077]
 195     or      phase, r0       ;[078]
 196     eor     x2, x1          ;[079]
 197     bst     x2, USBMINUS    ;[080]
 198     bld     shift, 6        ;[081] no need to check bitstuffing, we just had one
 199     in      r0, USBIN       ;[082] <-- phase
 200     rjmp    didUnstuff5     ;[083]
 201 ;   [---]                   ;[084]
 202                             ;[074]
 203
 204 unstuff6:                   ;[074]
 205     andi    x3, ~0x40       ;[075]
 206     in      x1, USBIN       ;[076] <-- bit 6 again
 207     ori     shift, 0x40     ;[077]
 208     nop2                    ;[078]
 209 ;   [---]                   ;[079]
 210     rjmp    didUnstuff6     ;[080]
 211 ;   [---]                   ;[081]
 212                             ;[071]
 213
 214 unstuff0:                   ;[013]
 215     eor     r0, x2          ;[014]
 216     or      phase, r0       ;[015]
 217     andi    x2, USBMASK     ;[016] check for SE0
 218     in      r0, USBIN       ;[017] <-- phase
 219     breq    didUnstuff0     ;[018] direct jump to se0 would be too long
 220     andi    x3, ~0x01       ;[019]
 221     ori     shift, 0x01     ;[020]
 222     mov     x1, x2          ;[021] mov existing sample
 223     in      x2, USBIN       ;[022] <-- bit 1 again
 224     rjmp    didUnstuff0     ;[023]
 225 ;   [---]                   ;[024]
 226                             ;[014]
 227
 228 unstuff1:                   ;[024]
 229     eor     r0, x1          ;[025]
 230     or      phase, r0       ;[026]
 231     andi    x3, ~0x02       ;[027]
 232     in      r0, USBIN       ;[028] <-- phase
 233     ori     shift, 0x02     ;[029]
 234     mov     x2, x1          ;[030]
 235     rjmp    didUnstuff1     ;[031]
 236 ;   [---]                   ;[032]
 237                             ;[022]
 238
 239 unstuff2:                   ;[035]
 240     eor     r0, x2          ;[036]
 241     or      phase, r0       ;[037]
 242     andi    x3, ~0x04       ;[038]
 243     in      r0, USBIN       ;[039] <-- phase
 244     ori     shift, 0x04     ;[040]
 245     mov     x1, x2          ;[041]
 246     rjmp    didUnstuff2     ;[042]
 247 ;   [---]                   ;[043]
 248                             ;[033]
 249
 250 unstuff3:                   ;[043]
 251     in      x2, USBIN       ;[044] <-- bit 3 again
 252     eor     r0, x2          ;[045]
 253     or      phase, r0       ;[046]
 254     andi    x3, ~0x08       ;[047]
 255     ori     shift, 0x08     ;[048]
 256     nop                     ;[049]
 257     in      r0, USBIN       ;[050] <-- phase
 258     rjmp    didUnstuff3     ;[051]
 259 ;   [---]                   ;[052]
 260                             ;[042]
 261
 262 unstuff4:                   ;[053]
 263     andi    x3, ~0x10       ;[054]
 264     in      x1, USBIN       ;[055] <-- bit 4 again
 265     ori     shift, 0x10     ;[056]
 266     rjmp    didUnstuff4     ;[057]
 267 ;   [---]                   ;[058]
 268                             ;[048]
 269
 270 rxLoop:                     ;[085]
 271     eor     x3, shift       ;[086] reconstruct: x3 is 0 at bit locations we changed, 1 at others
 272     in      x1, USBIN       ;[000] <-- bit 0
 273     st      y+, x3          ;[001]
 274 ;   [---]                   ;[002]
 275     eor     r0, x1          ;[003]
 276     or      phase, r0       ;[004]
 277     eor     x2, x1          ;[005]
 278     in      r0, USBIN       ;[006] <-- phase
 279     ser     x3              ;[007]
 280     bst     x2, USBMINUS    ;[008]
 281     bld     shift, 0        ;[009]
 282     andi    shift, 0xf9     ;[010]
 283 rxbit1:                     ;[   ]
 284     in      x2, USBIN       ;[011] <-- bit 1
 285     breq    unstuff0        ;[012] *** unstuff escape
 286     andi    x2, USBMASK     ;[013] SE0 check for bit 1
 287 didUnstuff0:                ;[   ] Z only set if we detected SE0 in bitstuff
 288     breq    se0             ;[014]
 289     eor     r0, x2          ;[015]
 290     or      phase, r0       ;[016]
 291     in      r0, USBIN       ;[017] <-- phase
 292     eor     x1, x2          ;[018]
 293     bst     x1, USBMINUS    ;[019]
 294     bld     shift, 1        ;[020]
 295     andi    shift, 0xf3     ;[021]
 296 didUnstuff1:                ;[   ]
 297     in      x1, USBIN       ;[022] <-- bit 2
 298     breq    unstuff1        ;[023] *** unstuff escape
 299     eor     r0, x1          ;[024]
 300     or      phase, r0       ;[025]
 301     subi    cnt, 1          ;[026] overflow check
 302     brcs    overflow        ;[027]
 303     in      r0, USBIN       ;[028] <-- phase
 304     eor     x2, x1          ;[029]
 305     bst     x2, USBMINUS    ;[030]
 306     bld     shift, 2        ;[031]
 307     andi    shift, 0xe7     ;[032]
 308 didUnstuff2:                ;[   ]
 309     in      x2, USBIN       ;[033] <-- bit 3
 310     breq    unstuff2        ;[034] *** unstuff escape
 311     eor     r0, x2          ;[035]
 312     or      phase, r0       ;[036]
 313     eor     x1, x2          ;[037]
 314     bst     x1, USBMINUS    ;[038]
 315     in      r0, USBIN       ;[039] <-- phase
 316     bld     shift, 3        ;[040]
 317     andi    shift, 0xcf     ;[041]
 318 didUnstuff3:                ;[   ]
 319     breq    unstuff3        ;[042] *** unstuff escape
 320     nop                     ;[043]
 321     in      x1, USBIN       ;[044] <-- bit 4
 322     eor     x2, x1          ;[045]
 323     bst     x2, USBMINUS    ;[046]
 324     bld     shift, 4        ;[047]
 325 didUnstuff4:                ;[   ]
 326     eor     r0, x1          ;[048]
 327     or      phase, r0       ;[049]
 328     in      r0, USBIN       ;[050] <-- phase
 329     andi    shift, 0x9f     ;[051]
 330     breq    unstuff4        ;[052] *** unstuff escape
 331     rjmp    continueWithBit5;[053]
 332 ;   [---]                   ;[054]
 333
 334 macro POP_STANDARD ; 16 cycles
 335     pop     cnt
 336     pop     x4
 337     pop     x3
 338     pop     x2
 339     pop     x1
 340     pop     shift
 341     pop     YH
 342     pop     r0
 343     endm
 344 macro POP_RETI     ; 5 cycles
 345     pop     YL
 346     out     SREG, YL
 347     pop     YL
 348     endm
 349
 350 #include "asmcommon.inc"
 351
 352
 353 ; USB spec says:
 354 ; idle = J
 355 ; J = (D+ = 0), (D- = 1)
 356 ; K = (D+ = 1), (D- = 0)
 357 ; Spec allows 7.5 bit times from EOP to SOP for replies
 358
 359 bitstuff7:
 360     eor     x1, x4          ;[4]
 361     ldi     x2, 0           ;[5]
 362     nop2                    ;[6] C is zero (brcc)
 363     rjmp    didStuff7       ;[8]
 364
 365 bitstuffN:
 366     eor     x1, x4          ;[5]
 367     ldi     x2, 0           ;[6]
 368     lpm                     ;[7] 3 cycle NOP, modifies r0
 369     out     USBOUT, x1      ;[10] <-- out
 370     rjmp    didStuffN       ;[0]
 371
 372 #define bitStatus   x3
 373
 374 sendNakAndReti:
 375     ldi     cnt, USBPID_NAK ;[-19]
 376     rjmp    sendCntAndReti  ;[-18]
 377 sendAckAndReti:
 378     ldi     cnt, USBPID_ACK ;[-17]
 379 sendCntAndReti:
 380     mov     r0, cnt         ;[-16]
 381     ldi     YL, 0           ;[-15] R0 address is 0
 382     ldi     YH, 0           ;[-14]
 383     ldi     cnt, 2          ;[-13]
 384 ;   rjmp    usbSendAndReti      fallthrough
 385
 386 ;usbSend:
 387 ;pointer to data in 'Y'
 388 ;number of bytes in 'cnt' -- including sync byte [range 2 ... 12]
 389 ;uses: x1...x4, shift, cnt, Y
 390 ;Numbers in brackets are time since first bit of sync pattern is sent
 391 usbSendAndReti:             ; 12 cycles until SOP
 392     in      x2, USBDDR      ;[-12]
 393     ori     x2, USBMASK     ;[-11]
 394     sbi     USBOUT, USBMINUS;[-10] prepare idle state; D+ and D- must have been 0 (no pullups)
 395     in      x1, USBOUT      ;[-8] port mirror for tx loop
 396     out     USBDDR, x2      ;[-7] <- acquire bus
 397 ; need not init x2 (bitstuff history) because sync starts with 0
 398     ldi     x4, USBMASK     ;[-6] exor mask
 399     ldi     shift, 0x80     ;[-5] sync byte is first byte sent
 400     ldi     bitStatus, 0xff ;[-4] init bit loop counter, works for up to 12 bytes
 401 byteloop:
 402 bitloop:
 403     sbrs    shift, 0        ;[8] [-3]
 404     eor     x1, x4          ;[9] [-2]
 405     out     USBOUT, x1      ;[10] [-1] <-- out
 406     ror     shift           ;[0]
 407     ror     x2              ;[1]
 408 didStuffN:
 409     cpi     x2, 0xfc        ;[2]
 410     brcc    bitstuffN       ;[3]
 411     nop                     ;[4]
 412     subi    bitStatus, 37   ;[5] 256 / 7 ~=~ 37
 413     brcc    bitloop         ;[6] when we leave the loop, bitStatus has almost the initial value
 414     sbrs    shift, 0        ;[7]
 415     eor     x1, x4          ;[8]
 416     ror     shift           ;[9]
 417 didStuff7:
 418     out     USBOUT, x1      ;[10] <-- out
 419     ror     x2              ;[0]
 420     cpi     x2, 0xfc        ;[1]
 421     brcc    bitstuff7       ;[2]
 422     ld      shift, y+       ;[3]
 423     dec     cnt             ;[5]
 424     brne    byteloop        ;[6]
 425 ;make SE0:
 426     cbr     x1, USBMASK     ;[7] prepare SE0 [spec says EOP may be 21 to 25 cycles]
 427     lds     x2, usbNewDeviceAddr;[8]
 428     lsl     x2              ;[10] we compare with left shifted address
 429     out     USBOUT, x1      ;[11] <-- out SE0 -- from now 2 bits = 22 cycles until bus idle
 430 ;2006-03-06: moved transfer of new address to usbDeviceAddr from C-Code to asm:
 431 ;set address only after data packet was sent, not after handshake
 432     subi    YL, 2           ;[0] Only assign address on data packets, not ACK/NAK in r0
 433     sbci    YH, 0           ;[1]
 434     breq    skipAddrAssign  ;[2]
 435     sts     usbDeviceAddr, x2; if not skipped: SE0 is one cycle longer
 436 skipAddrAssign:
 437 ;end of usbDeviceAddress transfer
 438     ldi     x2, 1<<USB_INTR_PENDING_BIT;[4] int0 occurred during TX -- clear pending flag
 439     USB_STORE_PENDING(x2)   ;[5]
 440     ori     x1, USBIDLE     ;[6]
 441     in      x2, USBDDR      ;[7]
 442     cbr     x2, USBMASK     ;[8] set both pins to input
 443     mov     x3, x1          ;[9]
 444     cbr     x3, USBMASK     ;[10] configure no pullup on both pins
 445     ldi     x4, 4           ;[11]
 446 se0Delay:
 447     dec     x4              ;[12] [15] [18] [21]
 448     brne    se0Delay        ;[13] [16] [19] [22]
 449     out     USBOUT, x1      ;[23] <-- out J (idle) -- end of SE0 (EOP signal)
 450     out     USBDDR, x2      ;[24] <-- release bus now
 451     out     USBOUT, x3      ;[25] <-- ensure no pull-up resistors are active
 452     rjmp    doReturn
 453