X-Git-Url: http://git.linex4red.de/pub/USBasp.git/blobdiff_plain/6ffa080eb257892c7cad9f80f8bfef99b4896082..39f1c0c136520a3f4746ad6381d1242979125ff3:/firmware/usbdrv/usbdrvasm165.S

diff --git a/firmware/usbdrv/usbdrvasm165.S b/firmware/usbdrv/usbdrvasm165.S
deleted file mode 100644
index 23261e813..000000000
--- a/firmware/usbdrv/usbdrvasm165.S
+++ /dev/null
@@ -1,574 +0,0 @@
-/* Name: usbdrvasm165.S
- * Project: AVR USB driver
- * Author: Christian Starkjohann
- * Creation Date: 2007-04-22
- * Tabsize: 4
- * Copyright: (c) 2007 by OBJECTIVE DEVELOPMENT Software GmbH
- * License: GNU GPL v2 (see License.txt) or proprietary (CommercialLicense.txt)
- * Revision: $Id$
- */
-
-/* Do not link this file! Link usbdrvasm.S instead, which includes the
- * appropriate implementation!
- */
-
-/*
-General Description:
-This file is the 16.5 MHz version of the USB driver. It is intended for the
-ATTiny45 and similar controllers running on 16.5 MHz internal RC oscillator.
-This version contains a phase locked loop in the receiver routine to cope with
-slight clock rate deviations of up to +/- 1%.
-
-See usbdrv.h for a description of the entire driver.
-
-Since almost all of this code is timing critical, don't change unless you
-really know what you are doing! Many parts require not only a maximum number
-of CPU cycles, but even an exact number of cycles!
-*/
-
-;Software-receiver engine. Strict timing! Don't change unless you can preserve timing!
-;interrupt response time: 4 cycles + insn running = 7 max if interrupts always enabled
-;max allowable interrupt latency: 59 cycles -> max 52 cycles interrupt disable
-;max stack usage: [ret(2), r0, SREG, YL, YH, shift, x1, x2, x3, x4, cnt] = 12 bytes
-;nominal frequency: 16.5 MHz -> 11 cycles per bit
-; 16.3125 MHz < F_CPU < 16.6875 MHz (+/- 1.1%)
-; Numbers in brackets are clocks counted from center of last sync bit
-; when instruction starts
-
-
-SIG_INTERRUPT0:
-;order of registers pushed: r0, SREG [sofError], YL, YH, shift, x1, x2, x3, x4, cnt
-    push    r0                  ;[-23] push only what is necessary to sync with edge ASAP
-    in      r0, SREG            ;[-21]
-    push    r0                  ;[-20]
-;----------------------------------------------------------------------------
-; Synchronize with sync pattern:
-;----------------------------------------------------------------------------
-;sync byte (D-) pattern LSb to MSb: 01010100 [1 = idle = J, 0 = K]
-;sync up with J to K edge during sync pattern -- use fastest possible loops
-;first part has no timeout because it waits for IDLE or SE1 (== disconnected)
-waitForJ:
-    sbis    USBIN, USBMINUS     ;[-18] wait for D- == 1
-    rjmp    waitForJ
-waitForK:
-;The following code results in a sampling window of < 1/4 bit which meets the spec.
-    sbis    USBIN, USBMINUS     ;[-15]
-    rjmp    foundK              ;[-14]
-    sbis    USBIN, USBMINUS
-    rjmp    foundK
-    sbis    USBIN, USBMINUS
-    rjmp    foundK
-    sbis    USBIN, USBMINUS
-    rjmp    foundK
-    sbis    USBIN, USBMINUS
-    rjmp    foundK
-    sbis    USBIN, USBMINUS
-    rjmp    foundK
-    rjmp    sofError
-foundK:                         ;[-12]
-;{3, 5} after falling D- edge, average delay: 4 cycles [we want 5 for center sampling]
-;we have 1 bit time for setup purposes, then sample again. Numbers in brackets
-;are cycles from center of first sync (double K) bit after the instruction
-    push    YL                  ;[-12]
-;   [---]                       ;[-11]
-    push    YH                  ;[-10]
-;   [---]                       ;[-9]
-    lds     YL, usbInputBufOffset;[-8]
-;   [---]                       ;[-7]
-    clr     YH                  ;[-6]
-    subi    YL, lo8(-(usbRxBuf));[-5] [rx loop init]
-    sbci    YH, hi8(-(usbRxBuf));[-4] [rx loop init]
-    mov     r0, x2              ;[-3] [rx loop init]
-    sbis    USBIN, USBMINUS     ;[-2] we want two bits K (sample 2 cycles too early)
-    rjmp    haveTwoBitsK        ;[-1]
-    pop     YH                  ;[0] undo the pushes from before
-    pop     YL                  ;[2]
-    rjmp    waitForK            ;[4] this was not the end of sync, retry
-; The entire loop from waitForK until rjmp waitForK above must not exceed two
-; bit times (= 22 cycles).
-
-;----------------------------------------------------------------------------
-; push more registers and initialize values while we sample the first bits:
-;----------------------------------------------------------------------------
-haveTwoBitsK:               ;[1]
-    push    shift           ;[1]
-    push    x1              ;[3]
-    push    x2              ;[5]
-    push    x3              ;[7]
-    ldi     shift, 0xff     ;[9] [rx loop init]
-    ori     x3, 0xff        ;[10] [rx loop init] == ser x3, clear zero flag
-
-    in      x1, USBIN       ;[11] <-- sample bit 0
-    bst     x1, USBMINUS    ;[12]
-    bld     shift, 0        ;[13]
-    push    x4              ;[14] == phase
-;   [---]                   ;[15]
-    push    cnt             ;[16]
-;   [---]                   ;[17]
-    ldi     phase, 0        ;[18] [rx loop init]
-    ldi     cnt, USB_BUFSIZE;[19] [rx loop init]
-    rjmp    rxbit1          ;[20]
-;   [---]                   ;[21]
-
-;----------------------------------------------------------------------------
-; Receiver loop (numbers in brackets are cycles within byte after instr)
-;----------------------------------------------------------------------------
-/*
-byte oriented operations done during loop:
-bit 0: store data
-bit 1: SE0 check
-bit 2: overflow check
-bit 3: catch up
-bit 4: rjmp to achieve conditional jump range
-bit 5: PLL
-bit 6: catch up
-bit 7: jump, fixup bitstuff
-; 87 [+ 2] cycles
-------------------------------------------------------------------
-*/
-continueWithBit5:
-    in      x2, USBIN       ;[055] <-- bit 5
-    eor     r0, x2          ;[056]
-    or      phase, r0       ;[057]
-    sbrc    phase, USBMINUS ;[058]
-    lpm                     ;[059] optional nop3; modifies r0
-    in      phase, USBIN    ;[060] <-- phase
-    eor     x1, x2          ;[061]
-    bst     x1, USBMINUS    ;[062]
-    bld     shift, 5        ;[063]
-    andi    shift, 0x3f     ;[064]
-    in      x1, USBIN       ;[065] <-- bit 6
-    breq    unstuff5        ;[066] *** unstuff escape
-    eor     phase, x1       ;[067]
-    eor     x2, x1          ;[068]
-    bst     x2, USBMINUS    ;[069]
-    bld     shift, 6        ;[070]
-didUnstuff6:                ;[   ]
-    in      r0, USBIN       ;[071] <-- phase
-    cpi     shift, 0x02     ;[072]
-    brlo    unstuff6        ;[073] *** unstuff escape
-didUnstuff5:                ;[   ]
-    nop2                    ;[074]
-;   [---]                   ;[075]
-    in      x2, USBIN       ;[076] <-- bit 7
-    eor     x1, x2          ;[077]
-    bst     x1, USBMINUS    ;[078]
-    bld     shift, 7        ;[079]
-didUnstuff7:                ;[   ]
-    eor     r0, x2          ;[080]
-    or      phase, r0       ;[081]
-    in      r0, USBIN       ;[082] <-- phase
-    cpi     shift, 0x04     ;[083]
-    brsh    rxLoop          ;[084]
-;   [---]                   ;[085]
-unstuff7:                   ;[   ]
-    andi    x3, ~0x80       ;[085]
-    ori     shift, 0x80     ;[086]
-    in      x2, USBIN       ;[087] <-- sample stuffed bit 7
-    nop                     ;[088]
-    rjmp    didUnstuff7     ;[089]
-;   [---]                   ;[090]
-                            ;[080]
-
-unstuff5:                   ;[067]
-    eor     phase, x1       ;[068]
-    andi    x3, ~0x20       ;[069]
-    ori     shift, 0x20     ;[070]
-    in      r0, USBIN       ;[071] <-- phase
-    mov     x2, x1          ;[072]
-    nop                     ;[073]
-    nop2                    ;[074]
-;   [---]                   ;[075]
-    in      x1, USBIN       ;[076] <-- bit 6
-    eor     r0, x1          ;[077]
-    or      phase, r0       ;[078]
-    eor     x2, x1          ;[079]
-    bst     x2, USBMINUS    ;[080]
-    bld     shift, 6        ;[081] no need to check bitstuffing, we just had one
-    in      r0, USBIN       ;[082] <-- phase
-    rjmp    didUnstuff5     ;[083]
-;   [---]                   ;[084]
-                            ;[074]
-
-unstuff6:                   ;[074]
-    andi    x3, ~0x40       ;[075]
-    in      x1, USBIN       ;[076] <-- bit 6 again
-    ori     shift, 0x40     ;[077]
-    nop2                    ;[078]
-;   [---]                   ;[079]
-    rjmp    didUnstuff6     ;[080]
-;   [---]                   ;[081]
-                            ;[071]
-
-unstuff0:                   ;[013]
-    eor     r0, x2          ;[014]
-    or      phase, r0       ;[015]
-    andi    x2, USBMASK     ;[016] check for SE0
-    in      r0, USBIN       ;[017] <-- phase
-    breq    didUnstuff0     ;[018] direct jump to se0 would be too long
-    andi    x3, ~0x01       ;[019]
-    ori     shift, 0x01     ;[020]
-    mov     x1, x2          ;[021] mov existing sample
-    in      x2, USBIN       ;[022] <-- bit 1 again
-    rjmp    didUnstuff0     ;[023]
-;   [---]                   ;[024]
-                            ;[014]
-
-unstuff1:                   ;[024]
-    eor     r0, x1          ;[025]
-    or      phase, r0       ;[026]
-    andi    x3, ~0x02       ;[027]
-    in      r0, USBIN       ;[028] <-- phase
-    ori     shift, 0x02     ;[029]
-    mov     x2, x1          ;[030]
-    rjmp    didUnstuff1     ;[031]
-;   [---]                   ;[032]
-                            ;[022]
-
-unstuff2:                   ;[035]
-    eor     r0, x2          ;[036]
-    or      phase, r0       ;[037]
-    andi    x3, ~0x04       ;[038]
-    in      r0, USBIN       ;[039] <-- phase
-    ori     shift, 0x04     ;[040]
-    mov     x1, x2          ;[041]
-    rjmp    didUnstuff2     ;[042]
-;   [---]                   ;[043]
-                            ;[033]
-
-unstuff3:                   ;[043]
-    in      x2, USBIN       ;[044] <-- bit 3 again
-    eor     r0, x2          ;[045]
-    or      phase, r0       ;[046]
-    andi    x3, ~0x08       ;[047]
-    ori     shift, 0x08     ;[048]
-    nop                     ;[049]
-    in      r0, USBIN       ;[050] <-- phase
-    rjmp    didUnstuff3     ;[051]
-;   [---]                   ;[052]
-                            ;[042]
-
-unstuff4:                   ;[053]
-    andi    x3, ~0x10       ;[054]
-    in      x1, USBIN       ;[055] <-- bit 4 again
-    ori     shift, 0x10     ;[056]
-    rjmp    didUnstuff4     ;[057]
-;   [---]                   ;[058]
-                            ;[048]
-
-rxLoop:                     ;[085]
-    eor     x3, shift       ;[086] reconstruct: x3 is 0 at bit locations we changed, 1 at others
-    in      x1, USBIN       ;[000] <-- bit 0
-    st      y+, x3          ;[001]
-;   [---]                   ;[002]
-    eor     r0, x1          ;[003]
-    or      phase, r0       ;[004]
-    eor     x2, x1          ;[005]
-    in      r0, USBIN       ;[006] <-- phase
-    ser     x3              ;[007]
-    bst     x2, USBMINUS    ;[008]
-    bld     shift, 0        ;[009]
-    andi    shift, 0xf9     ;[010]
-rxbit1:                     ;[   ]
-    in      x2, USBIN       ;[011] <-- bit 1
-    breq    unstuff0        ;[012] *** unstuff escape
-    andi    x2, USBMASK     ;[013] SE0 check for bit 1
-didUnstuff0:                ;[   ] Z only set if we detected SE0 in bitstuff
-    breq    se0             ;[014]
-    eor     r0, x2          ;[015]
-    or      phase, r0       ;[016]
-    in      r0, USBIN       ;[017] <-- phase
-    eor     x1, x2          ;[018]
-    bst     x1, USBMINUS    ;[019]
-    bld     shift, 1        ;[020]
-    andi    shift, 0xf3     ;[021]
-didUnstuff1:                ;[   ]
-    in      x1, USBIN       ;[022] <-- bit 2
-    breq    unstuff1        ;[023] *** unstuff escape
-    eor     r0, x1          ;[024]
-    or      phase, r0       ;[025]
-    subi    cnt, 1          ;[026] overflow check
-    brcs    overflow        ;[027]
-    in      r0, USBIN       ;[028] <-- phase
-    eor     x2, x1          ;[029]
-    bst     x2, USBMINUS    ;[030]
-    bld     shift, 2        ;[031]
-    andi    shift, 0xe7     ;[032]
-didUnstuff2:                ;[   ]
-    in      x2, USBIN       ;[033] <-- bit 3
-    breq    unstuff2        ;[034] *** unstuff escape
-    eor     r0, x2          ;[035]
-    or      phase, r0       ;[036]
-    eor     x1, x2          ;[037]
-    bst     x1, USBMINUS    ;[038]
-    in      r0, USBIN       ;[039] <-- phase
-    bld     shift, 3        ;[040]
-    andi    shift, 0xcf     ;[041]
-didUnstuff3:                ;[   ]
-    breq    unstuff3        ;[042] *** unstuff escape
-    nop                     ;[043]
-    in      x1, USBIN       ;[044] <-- bit 4
-    eor     x2, x1          ;[045]
-    bst     x2, USBMINUS    ;[046]
-    bld     shift, 4        ;[047]
-didUnstuff4:                ;[   ]
-    eor     r0, x1          ;[048]
-    or      phase, r0       ;[049]
-    in      r0, USBIN       ;[050] <-- phase
-    andi    shift, 0x9f     ;[051]
-    breq    unstuff4        ;[052] *** unstuff escape
-    rjmp    continueWithBit5;[053]
-;   [---]                   ;[054]
-
-;----------------------------------------------------------------------------
-; Processing of received packet (numbers in brackets are cycles after center of SE0)
-;----------------------------------------------------------------------------
-;This is the only non-error exit point for the software receiver loop
-;we don't check any CRCs here because there is no time left.
-#define token   x1
-se0:
-    subi    cnt, USB_BUFSIZE    ;[5]
-    neg     cnt                 ;[6]
-    cpi     cnt, 3              ;[7]
-    ldi     x2, 1<<USB_INTR_PENDING_BIT ;[8]
-    out     USB_INTR_PENDING, x2;[9] clear pending intr and check flag later. SE0 should be over.
-    brlo    doReturn            ;[10] this is probably an ACK, NAK or similar packet
-    sub     YL, cnt             ;[11]
-    sbci    YH, 0               ;[12]
-    ld      token, y            ;[13]
-    cpi     token, USBPID_DATA0 ;[15]
-    breq    handleData          ;[16]
-    cpi     token, USBPID_DATA1 ;[17]
-    breq    handleData          ;[18]
-    ldd     x2, y+1             ;[19] ADDR and 1 bit endpoint number
-    mov     x3, x2              ;[21] store for endpoint number
-    andi    x2, 0x7f            ;[22] x2 is now ADDR
-    lds     shift, usbDeviceAddr;[23]
-    cp      x2, shift           ;[25]
-overflow:                       ; This is a hack: brcs overflow will never have Z flag set
-    brne    ignorePacket        ;[26] packet for different address
-    cpi     token, USBPID_IN    ;[27]
-    breq    handleIn            ;[28]
-    cpi     token, USBPID_SETUP ;[29]
-    breq    handleSetupOrOut    ;[30]
-    cpi     token, USBPID_OUT   ;[31]
-    breq    handleSetupOrOut    ;[32]
-;   rjmp    ignorePacket        ;fallthrough, should not happen anyway.
-
-ignorePacket:
-    clr     shift
-    sts     usbCurrentTok, shift
-doReturn:
-    pop     cnt
-    pop     x4
-    pop     x3
-    pop     x2
-    pop     x1
-    pop     shift
-    pop     YH
-    pop     YL
-sofError:
-    pop     r0
-    out     SREG, r0
-    pop     r0
-    reti
-
-#if USB_CFG_HAVE_INTRIN_ENDPOINT && USB_CFG_HAVE_INTRIN_ENDPOINT3
-handleIn3:
-    lds     cnt, usbTxLen3      ;[43]
-    sbrc    cnt, 4              ;[45]
-    rjmp    sendCntAndReti      ;[46] 48 + 16 = 64 until SOP
-    sts     usbTxLen3, x1       ;[47] x1 == USBPID_NAK from above
-    ldi     YL, lo8(usbTxBuf3)  ;[49]
-    ldi     YH, hi8(usbTxBuf3)  ;[50]
-    rjmp    usbSendAndReti      ;[51] 53 + 12 = 65 until SOP
-#endif
-
-;Setup and Out are followed by a data packet two bit times (16 cycles) after
-;the end of SE0. The sync code allows up to 40 cycles delay from the start of
-;the sync pattern until the first bit is sampled. That's a total of 56 cycles.
-handleSetupOrOut:               ;[34]
-#if USB_CFG_IMPLEMENT_FN_WRITEOUT   /* if we have data for second OUT endpoint, set usbCurrentTok to -1 */
-    sbrc    x3, 7               ;[34] skip if endpoint 0
-    ldi     token, -1           ;[35] indicate that this is endpoint 1 OUT
-#endif
-    sts     usbCurrentTok, token;[36]
-    pop     cnt                 ;[38]
-    pop     x4                  ;[40]
-    pop     x3                  ;[42]
-    pop     x2                  ;[44]
-    pop     x1                  ;[46]
-    pop     shift               ;[48]
-    pop     YH                  ;[50]
-    pop     YL                  ;[52]
-    in      r0, USB_INTR_PENDING;[54]
-    sbrc    r0, USB_INTR_PENDING_BIT;[55] check whether data is already arriving
-    rjmp    waitForJ            ;[56] save the pops and pushes -- a new interrupt is aready pending
-    rjmp    sofError            ;[57] not an error, but it does the pops and reti we want
-
-
-handleData:
-    lds     token, usbCurrentTok;[20]
-    tst     token               ;[22]
-    breq    doReturn            ;[23]
-    lds     x2, usbRxLen        ;[24]
-    tst     x2                  ;[26]
-    brne    sendNakAndReti      ;[27]
-; 2006-03-11: The following two lines fix a problem where the device was not
-; recognized if usbPoll() was called less frequently than once every 4 ms.
-    cpi     cnt, 4              ;[28] zero sized data packets are status phase only -- ignore and ack
-    brmi    sendAckAndReti      ;[29] keep rx buffer clean -- we must not NAK next SETUP
-    sts     usbRxLen, cnt       ;[30] store received data, swap buffers
-    sts     usbRxToken, token   ;[32]
-    lds     x2, usbInputBufOffset;[34] swap buffers
-    ldi     cnt, USB_BUFSIZE    ;[36]
-    sub     cnt, x2             ;[37]
-    sts     usbInputBufOffset, cnt;[38] buffers now swapped
-    rjmp    sendAckAndReti      ;[40] 42 + 17 = 59 until SOP
-
-handleIn:
-;We don't send any data as long as the C code has not processed the current
-;input data and potentially updated the output data. That's more efficient
-;in terms of code size than clearing the tx buffers when a packet is received.
-    lds     x1, usbRxLen        ;[30]
-    cpi     x1, 1               ;[32] negative values are flow control, 0 means "buffer free"
-    brge    sendNakAndReti      ;[33] unprocessed input packet?
-    ldi     x1, USBPID_NAK      ;[34] prepare value for usbTxLen
-#if USB_CFG_HAVE_INTRIN_ENDPOINT
-    sbrc    x3, 7               ;[35] x3 contains addr + endpoint
-    rjmp    handleIn1           ;[36]
-#endif
-    lds     cnt, usbTxLen       ;[37]
-    sbrc    cnt, 4              ;[39] all handshake tokens have bit 4 set
-    rjmp    sendCntAndReti      ;[40] 42 + 16 = 58 until SOP
-    sts     usbTxLen, x1        ;[41] x1 == USBPID_NAK from above
-    ldi     YL, lo8(usbTxBuf)   ;[43]
-    ldi     YH, hi8(usbTxBuf)   ;[44]
-    rjmp    usbSendAndReti      ;[45] 47 + 12 = 59 until SOP
-
-; Comment about when to set usbTxLen to USBPID_NAK:
-; We should set it back when we receive the ACK from the host. This would
-; be simple to implement: One static variable which stores whether the last
-; tx was for endpoint 0 or 1 and a compare in the receiver to distinguish the
-; ACK. However, we set it back immediately when we send the package,
-; assuming that no error occurs and the host sends an ACK. We save one byte
-; RAM this way and avoid potential problems with endless retries. The rest of
-; the driver assumes error-free transfers anyway.
-
-#if USB_CFG_HAVE_INTRIN_ENDPOINT    /* placed here due to relative jump range */
-handleIn1:                      ;[38]
-#if USB_CFG_HAVE_INTRIN_ENDPOINT3
-; 2006-06-10 as suggested by O.Tamura: support second INTR IN / BULK IN endpoint
-    ldd     x2, y+2             ;[38]
-    sbrc    x2, 0               ;[40]
-    rjmp    handleIn3           ;[41]
-#endif
-    lds     cnt, usbTxLen1      ;[42]
-    sbrc    cnt, 4              ;[44] all handshake tokens have bit 4 set
-    rjmp    sendCntAndReti      ;[45] 47 + 16 = 63 until SOP
-    sts     usbTxLen1, x1       ;[46] x1 == USBPID_NAK from above
-    ldi     YL, lo8(usbTxBuf1)  ;[48]
-    ldi     YH, hi8(usbTxBuf1)  ;[49]
-    rjmp    usbSendAndReti      ;[50] 52 + 12 + 64 until SOP
-#endif
-
-
-; USB spec says:
-; idle = J
-; J = (D+ = 0), (D- = 1)
-; K = (D+ = 1), (D- = 0)
-; Spec allows 7.5 bit times from EOP to SOP for replies
-
-bitstuff7:
-    eor     x1, x4          ;[4]
-    ldi     x2, 0           ;[5]
-    nop2                    ;[6] C is zero (brcc)
-    rjmp    didStuff7       ;[8]
-
-bitstuffN:
-    eor     x1, x4          ;[5]
-    ldi     x2, 0           ;[6]
-    lpm                     ;[7] 3 cycle NOP, modifies r0
-    out     USBOUT, x1      ;[10] <-- out
-    rjmp    didStuffN       ;[0]
-
-#define bitStatus   x3
-
-sendNakAndReti:
-    ldi     cnt, USBPID_NAK ;[-19]
-    rjmp    sendCntAndReti  ;[-18]
-sendAckAndReti:
-    ldi     cnt, USBPID_ACK ;[-17]
-sendCntAndReti:
-    mov     r0, cnt         ;[-16]
-    ldi     YL, 0           ;[-15] R0 address is 0
-    ldi     YH, 0           ;[-14]
-    ldi     cnt, 2          ;[-13]
-;   rjmp    usbSendAndReti      fallthrough
-
-;usbSend:
-;pointer to data in 'Y'
-;number of bytes in 'cnt' -- including sync byte [range 2 ... 12]
-;uses: x1...x4, shift, cnt, Y
-;Numbers in brackets are time since first bit of sync pattern is sent
-usbSendAndReti:             ; 12 cycles until SOP
-    in      x2, USBDDR      ;[-12]
-    ori     x2, USBMASK     ;[-11]
-    sbi     USBOUT, USBMINUS;[-10] prepare idle state; D+ and D- must have been 0 (no pullups)
-    in      x1, USBOUT      ;[-8] port mirror for tx loop
-    out     USBDDR, x2      ;[-7] <- acquire bus
-; need not init x2 (bitstuff history) because sync starts with 0
-    ldi     x4, USBMASK     ;[-6] exor mask
-    ldi     shift, 0x80     ;[-5] sync byte is first byte sent
-    ldi     bitStatus, 0xff ;[-4] init bit loop counter, works for up to 12 bytes
-byteloop:
-bitloop:
-    sbrs    shift, 0        ;[8] [-3]
-    eor     x1, x4          ;[9] [-2]
-    out     USBOUT, x1      ;[10] [-1] <-- out
-    ror     shift           ;[0]
-    ror     x2              ;[1]
-didStuffN:
-    cpi     x2, 0xfc        ;[2]
-    brcc    bitstuffN       ;[3]
-    nop                     ;[4]
-    subi    bitStatus, 37   ;[5] 256 / 7 ~=~ 37
-    brcc    bitloop         ;[6] when we leave the loop, bitStatus has almost the initial value
-    sbrs    shift, 0        ;[7]
-    eor     x1, x4          ;[8]
-    ror     shift           ;[9]
-didStuff7:
-    out     USBOUT, x1      ;[10] <-- out
-    ror     x2              ;[0]
-    cpi     x2, 0xfc        ;[1]
-    brcc    bitstuff7       ;[2]
-    ld      shift, y+       ;[3]
-    dec     cnt             ;[5]
-    brne    byteloop        ;[6]
-;make SE0:
-    cbr     x1, USBMASK     ;[7] prepare SE0 [spec says EOP may be 21 to 25 cycles]
-    lds     x2, usbNewDeviceAddr;[8]
-    out     USBOUT, x1      ;[10] <-- out SE0 -- from now 2 bits = 22 cycles until bus idle
-;2006-03-06: moved transfer of new address to usbDeviceAddr from C-Code to asm:
-;set address only after data packet was sent, not after handshake
-    subi    YL, 2           ;[0]
-    sbci    YH, 0           ;[1]
-    breq    skipAddrAssign  ;[2]
-    sts     usbDeviceAddr, x2; if not skipped: SE0 is one cycle longer
-skipAddrAssign:
-;end of usbDeviceAddress transfer
-    ldi     x2, 1<<USB_INTR_PENDING_BIT;[4] int0 occurred during TX -- clear pending flag
-    out     USB_INTR_PENDING, x2;[5]
-    ori     x1, USBIDLE     ;[6]
-    in      x2, USBDDR      ;[7]
-    cbr     x2, USBMASK     ;[8] set both pins to input
-    mov     x3, x1          ;[9]
-    cbr     x3, USBMASK     ;[10] configure no pullup on both pins
-    ldi     x4, 4           ;[11]
-se0Delay:
-    dec     x4              ;[12] [15] [18] [21]
-    brne    se0Delay        ;[13] [16] [19] [22]
-    out     USBOUT, x1      ;[23] <-- out J (idle) -- end of SE0 (EOP signal)
-    out     USBDDR, x2      ;[24] <-- release bus now
-    out     USBOUT, x3      ;[25] <-- ensure no pull-up resistors are active
-    rjmp    doReturn