--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/usbdrv/usbdrvasm128.inc Thu Feb 16 14:40:23 2017 +0100
@@ -0,0 +1,749 @@
+/* Name: usbdrvasm128.inc
+ * Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers
+ * Author: Christian Starkjohann
+ * Creation Date: 2008-10-11
+ * Tabsize: 4
+ * Copyright: (c) 2008 by OBJECTIVE DEVELOPMENT Software GmbH
+ * License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt)
+ */
+
+/* Do not link this file! Link usbdrvasm.S instead, which includes the
+ * appropriate implementation!
+ */
+
+/*
+General Description:
+This file is the 12.8 MHz version of the USB driver. It is intended for use
+with the internal RC oscillator. Although 12.8 MHz is outside the guaranteed
+calibration range of the oscillator, almost all AVRs can reach this frequency.
+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.
+
+LIMITATIONS
+===========
+Although it may seem very handy to save the crystal and use the internal
+RC oscillator of the CPU, this method (and this module) has some serious
+limitations:
+(1) The guaranteed calibration range of the oscillator is only 8.1 MHz.
+They typical range is 14.5 MHz and most AVRs can actually reach this rate.
+(2) Writing EEPROM and Flash may be unreliable (short data lifetime) since
+the write procedure is timed from the RC oscillator.
+(3) End Of Packet detection (SE0) should be in bit 1, bit it is only checked
+if bits 0 and 1 both read as 0 on D- and D+ read as 0 in the middle. This may
+cause problems with old hubs which delay SE0 by up to one cycle.
+(4) Code size is much larger than that of the other modules.
+
+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!
+
+Implementation notes:
+======================
+min frequency: 67 cycles for 8 bit -> 12.5625 MHz
+max frequency: 69.286 cycles for 8 bit -> 12.99 MHz
+nominal frequency: 12.77 MHz ( = sqrt(min * max))
+
+sampling positions: (next even number in range [+/- 0.5])
+cycle index range: 0 ... 66
+bits:
+.5, 8.875, 17.25, 25.625, 34, 42.375, 50.75, 59.125
+[0/1], [9], [17], [25/+26], [34], [+42/43], [51], [59]
+
+bit number: 0 1 2 3 4 5 6 7
+spare cycles 1 2 1 2 1 1 1 0
+
+operations to perform: duration cycle
+ ----------------
+ eor fix, shift 1 -> 00
+ andi phase, USBMASK 1 -> 08
+ breq se0 1 -> 16 (moved to 11)
+ st y+, data 2 -> 24, 25
+ mov data, fix 1 -> 33
+ ser data 1 -> 41
+ subi cnt, 1 1 -> 49
+ brcs overflow 1 -> 50
+
+layout of samples and operations:
+[##] = sample bit
+<##> = sample phase
+*##* = operation
+
+0: *00* [01] 02 03 04 <05> 06 07
+1: *08* [09] 10 11 12 <13> 14 15 *16*
+2: [17] 18 19 20 <21> 22 23
+3: *24* *25* [26] 27 28 29 <30> 31 32
+4: *33* [34] 35 36 37 <38> 39 40
+5: *41* [42] 43 44 45 <46> 47 48
+6: *49* *50* [51] 52 53 54 <55> 56 57 58
+7: [59] 60 61 62 <63> 64 65 66
+*****************************************************************************/
+
+/* we prefer positive expressions (do if condition) instead of negative
+ * (skip if condition), therefore use defines for skip instructions:
+ */
+#define ifioclr sbis
+#define ifioset sbic
+#define ifrclr sbrs
+#define ifrset sbrc
+
+/* The registers "fix" and "data" swap their meaning during the loop. Use
+ * defines to keep their name constant.
+ */
+#define fix x2
+#define data x1
+#undef phase /* phase has a default definition to x4 */
+#define phase x3
+
+
+USB_INTR_VECTOR:
+;order of registers pushed: YL, SREG [sofError], YH, shift, x1, x2, x3, cnt, r0
+ push YL ;2 push only what is necessary to sync with edge ASAP
+ in YL, SREG ;1
+ push YL ;2
+;----------------------------------------------------------------------------
+; 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
+;The first part waits at most 1 bit long since we must be in sync pattern.
+;YL is guarenteed to be < 0x80 because I flag is clear. When we jump to
+;waitForJ, ensure that this prerequisite is met.
+waitForJ:
+ inc YL
+ sbis USBIN, USBMINUS
+ brne waitForJ ; just make sure we have ANY timeout
+waitForK:
+;The following code results in a sampling window of 1/4 bit which meets the spec.
+ sbis USBIN, USBMINUS
+ rjmp foundK
+ sbis USBIN, USBMINUS
+ rjmp foundK
+ sbis USBIN, USBMINUS
+ rjmp foundK
+ sbis USBIN, USBMINUS
+ rjmp foundK
+ sbis USBIN, USBMINUS ;[0]
+ rjmp foundK ;[1]
+#if USB_COUNT_SOF
+ lds YL, usbSofCount
+ inc YL
+ sts usbSofCount, YL
+#endif /* USB_COUNT_SOF */
+#ifdef USB_SOF_HOOK
+ USB_SOF_HOOK
+#endif
+ rjmp sofError
+
+foundK:
+;{3, 5} after falling D- edge, average delay: 4 cycles [we want 4 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 YH ;[2]
+ lds YL, usbInputBufOffset;[4]
+ clr YH ;[6]
+ subi YL, lo8(-(usbRxBuf));[7]
+ sbci YH, hi8(-(usbRxBuf));[8]
+
+ sbis USBIN, USBMINUS ;[9] we want two bits K [we want to sample at 8 + 4 - 1.5 = 10.5]
+ rjmp haveTwoBitsK ;[10]
+ pop YH ;[11] undo the push from before
+ rjmp waitForK ;[13] this was not the end of sync, retry
+haveTwoBitsK:
+;----------------------------------------------------------------------------
+; push more registers and initialize values while we sample the first bits:
+;----------------------------------------------------------------------------
+#define fix x2
+#define data x1
+
+ push shift ;[12]
+ push x1 ;[14]
+ push x2 ;[16]
+ ldi shift, 0x80 ;[18] prevent bit-unstuffing but init low bits to 0
+ ifioset USBIN, USBMINUS ;[19] [01] <--- bit 0 [10.5 + 8 = 18.5]
+ ori shift, 1<<0 ;[02]
+ push x3 ;[03]
+ push cnt ;[05]
+ push r0 ;[07]
+ ifioset USBIN, USBMINUS ;[09] <--- bit 1
+ ori shift, 1<<1 ;[10]
+ ser fix ;[11]
+ ldi cnt, USB_BUFSIZE ;[12]
+ mov data, shift ;[13]
+ lsl shift ;[14]
+ nop2 ;[15]
+ ifioset USBIN, USBMINUS ;[17] <--- bit 2
+ ori data, 3<<2 ;[18] store in bit 2 AND bit 3
+ eor shift, data ;[19] do nrzi decoding
+ andi data, 1<<3 ;[20]
+ in phase, USBIN ;[21] <- phase
+ brne jumpToEntryAfterSet ;[22] if USBMINS at bit 3 was 1
+ nop ;[23]
+ rjmp entryAfterClr ;[24]
+jumpToEntryAfterSet:
+ rjmp entryAfterSet ;[24]
+
+;----------------------------------------------------------------------------
+; Receiver loop (numbers in brackets are cycles within byte after instr)
+;----------------------------------------------------------------------------
+#undef fix
+#define fix x1
+#undef data
+#define data x2
+
+bit7IsSet:
+ ifrclr phase, USBMINUS ;[62] check phase only if D- changed
+ lpm ;[63]
+ in phase, USBIN ;[64] <- phase (one cycle too late)
+ ori shift, 1 << 7 ;[65]
+ nop ;[66]
+;;;;rjmp bit0AfterSet ; -> [00] == [67] moved block up to save jump
+bit0AfterSet:
+ eor fix, shift ;[00]
+#undef fix
+#define fix x2
+#undef data
+#define data x1 /* we now have result in data, fix is reset to 0xff */
+ ifioclr USBIN, USBMINUS ;[01] <--- sample 0
+ rjmp bit0IsClr ;[02]
+ andi shift, ~(7 << 0) ;[03]
+ breq unstuff0s ;[04]
+ in phase, USBIN ;[05] <- phase
+ rjmp bit1AfterSet ;[06]
+unstuff0s:
+ in phase, USBIN ;[06] <- phase (one cycle too late)
+ andi fix, ~(1 << 0) ;[07]
+ ifioclr USBIN, USBMINUS ;[00]
+ ifioset USBIN, USBPLUS ;[01]
+ rjmp bit0IsClr ;[02] executed if first expr false or second true
+se0AndStore: ; executed only if both bits 0
+ st y+, x1 ;[15/17] cycles after start of byte
+ rjmp se0 ;[17/19]
+
+bit0IsClr:
+ ifrset phase, USBMINUS ;[04] check phase only if D- changed
+ lpm ;[05]
+ in phase, USBIN ;[06] <- phase (one cycle too late)
+ ori shift, 1 << 0 ;[07]
+bit1AfterClr:
+ andi phase, USBMASK ;[08]
+ ifioset USBIN, USBMINUS ;[09] <--- sample 1
+ rjmp bit1IsSet ;[10]
+ breq se0AndStore ;[11] if D- was 0 in bits 0 AND 1 and D+ was 0 in between, we have SE0
+ andi shift, ~(7 << 1) ;[12]
+ in phase, USBIN ;[13] <- phase
+ breq unstuff1c ;[14]
+ rjmp bit2AfterClr ;[15]
+unstuff1c:
+ andi fix, ~(1 << 1) ;[16]
+ nop2 ;[08]
+ nop2 ;[10]
+bit1IsSet:
+ ifrclr phase, USBMINUS ;[12] check phase only if D- changed
+ lpm ;[13]
+ in phase, USBIN ;[14] <- phase (one cycle too late)
+ ori shift, 1 << 1 ;[15]
+ nop ;[16]
+bit2AfterSet:
+ ifioclr USBIN, USBMINUS ;[17] <--- sample 2
+ rjmp bit2IsClr ;[18]
+ andi shift, ~(7 << 2) ;[19]
+ breq unstuff2s ;[20]
+ in phase, USBIN ;[21] <- phase
+ rjmp bit3AfterSet ;[22]
+unstuff2s:
+ in phase, USBIN ;[22] <- phase (one cycle too late)
+ andi fix, ~(1 << 2) ;[23]
+ nop2 ;[16]
+ nop2 ;[18]
+bit2IsClr:
+ ifrset phase, USBMINUS ;[20] check phase only if D- changed
+ lpm ;[21]
+ in phase, USBIN ;[22] <- phase (one cycle too late)
+ ori shift, 1 << 2 ;[23]
+bit3AfterClr:
+ st y+, data ;[24]
+entryAfterClr:
+ ifioset USBIN, USBMINUS ;[26] <--- sample 3
+ rjmp bit3IsSet ;[27]
+ andi shift, ~(7 << 3) ;[28]
+ breq unstuff3c ;[29]
+ in phase, USBIN ;[30] <- phase
+ rjmp bit4AfterClr ;[31]
+unstuff3c:
+ in phase, USBIN ;[31] <- phase (one cycle too late)
+ andi fix, ~(1 << 3) ;[32]
+ nop2 ;[25]
+ nop2 ;[27]
+bit3IsSet:
+ ifrclr phase, USBMINUS ;[29] check phase only if D- changed
+ lpm ;[30]
+ in phase, USBIN ;[31] <- phase (one cycle too late)
+ ori shift, 1 << 3 ;[32]
+bit4AfterSet:
+ mov data, fix ;[33] undo this move by swapping defines
+#undef fix
+#define fix x1
+#undef data
+#define data x2
+ ifioclr USBIN, USBMINUS ;[34] <--- sample 4
+ rjmp bit4IsClr ;[35]
+ andi shift, ~(7 << 4) ;[36]
+ breq unstuff4s ;[37]
+ in phase, USBIN ;[38] <- phase
+ rjmp bit5AfterSet ;[39]
+unstuff4s:
+ in phase, USBIN ;[39] <- phase (one cycle too late)
+ andi fix, ~(1 << 4) ;[40]
+ nop2 ;[33]
+ nop2 ;[35]
+bit4IsClr:
+ ifrset phase, USBMINUS ;[37] check phase only if D- changed
+ lpm ;[38]
+ in phase, USBIN ;[39] <- phase (one cycle too late)
+ ori shift, 1 << 4 ;[40]
+bit5AfterClr:
+ ser data ;[41]
+ ifioset USBIN, USBMINUS ;[42] <--- sample 5
+ rjmp bit5IsSet ;[43]
+ andi shift, ~(7 << 5) ;[44]
+ breq unstuff5c ;[45]
+ in phase, USBIN ;[46] <- phase
+ rjmp bit6AfterClr ;[47]
+unstuff5c:
+ in phase, USBIN ;[47] <- phase (one cycle too late)
+ andi fix, ~(1 << 5) ;[48]
+ nop2 ;[41]
+ nop2 ;[43]
+bit5IsSet:
+ ifrclr phase, USBMINUS ;[45] check phase only if D- changed
+ lpm ;[46]
+ in phase, USBIN ;[47] <- phase (one cycle too late)
+ ori shift, 1 << 5 ;[48]
+bit6AfterSet:
+ subi cnt, 1 ;[49]
+ brcs jumpToOverflow ;[50]
+ ifioclr USBIN, USBMINUS ;[51] <--- sample 6
+ rjmp bit6IsClr ;[52]
+ andi shift, ~(3 << 6) ;[53]
+ cpi shift, 2 ;[54]
+ in phase, USBIN ;[55] <- phase
+ brlt unstuff6s ;[56]
+ rjmp bit7AfterSet ;[57]
+
+jumpToOverflow:
+ rjmp overflow
+
+unstuff6s:
+ andi fix, ~(1 << 6) ;[50]
+ lpm ;[51]
+bit6IsClr:
+ ifrset phase, USBMINUS ;[54] check phase only if D- changed
+ lpm ;[55]
+ in phase, USBIN ;[56] <- phase (one cycle too late)
+ ori shift, 1 << 6 ;[57]
+ nop ;[58]
+bit7AfterClr:
+ ifioset USBIN, USBMINUS ;[59] <--- sample 7
+ rjmp bit7IsSet ;[60]
+ andi shift, ~(1 << 7) ;[61]
+ cpi shift, 4 ;[62]
+ in phase, USBIN ;[63] <- phase
+ brlt unstuff7c ;[64]
+ rjmp bit0AfterClr ;[65] -> [00] == [67]
+unstuff7c:
+ andi fix, ~(1 << 7) ;[58]
+ nop ;[59]
+ rjmp bit7IsSet ;[60]
+
+bit7IsClr:
+ ifrset phase, USBMINUS ;[62] check phase only if D- changed
+ lpm ;[63]
+ in phase, USBIN ;[64] <- phase (one cycle too late)
+ ori shift, 1 << 7 ;[65]
+ nop ;[66]
+;;;;rjmp bit0AfterClr ; -> [00] == [67] moved block up to save jump
+bit0AfterClr:
+ eor fix, shift ;[00]
+#undef fix
+#define fix x2
+#undef data
+#define data x1 /* we now have result in data, fix is reset to 0xff */
+ ifioset USBIN, USBMINUS ;[01] <--- sample 0
+ rjmp bit0IsSet ;[02]
+ andi shift, ~(7 << 0) ;[03]
+ breq unstuff0c ;[04]
+ in phase, USBIN ;[05] <- phase
+ rjmp bit1AfterClr ;[06]
+unstuff0c:
+ in phase, USBIN ;[06] <- phase (one cycle too late)
+ andi fix, ~(1 << 0) ;[07]
+ ifioclr USBIN, USBMINUS ;[00]
+ ifioset USBIN, USBPLUS ;[01]
+ rjmp bit0IsSet ;[02] executed if first expr false or second true
+ rjmp se0AndStore ;[03] executed only if both bits 0
+bit0IsSet:
+ ifrclr phase, USBMINUS ;[04] check phase only if D- changed
+ lpm ;[05]
+ in phase, USBIN ;[06] <- phase (one cycle too late)
+ ori shift, 1 << 0 ;[07]
+bit1AfterSet:
+ andi shift, ~(7 << 1) ;[08] compensated by "ori shift, 1<<1" if bit1IsClr
+ ifioclr USBIN, USBMINUS ;[09] <--- sample 1
+ rjmp bit1IsClr ;[10]
+ breq unstuff1s ;[11]
+ nop2 ;[12] do not check for SE0 if bit 0 was 1
+ in phase, USBIN ;[14] <- phase (one cycle too late)
+ rjmp bit2AfterSet ;[15]
+unstuff1s:
+ in phase, USBIN ;[13] <- phase
+ andi fix, ~(1 << 1) ;[14]
+ lpm ;[07]
+ nop2 ;[10]
+bit1IsClr:
+ ifrset phase, USBMINUS ;[12] check phase only if D- changed
+ lpm ;[13]
+ in phase, USBIN ;[14] <- phase (one cycle too late)
+ ori shift, 1 << 1 ;[15]
+ nop ;[16]
+bit2AfterClr:
+ ifioset USBIN, USBMINUS ;[17] <--- sample 2
+ rjmp bit2IsSet ;[18]
+ andi shift, ~(7 << 2) ;[19]
+ breq unstuff2c ;[20]
+ in phase, USBIN ;[21] <- phase
+ rjmp bit3AfterClr ;[22]
+unstuff2c:
+ in phase, USBIN ;[22] <- phase (one cycle too late)
+ andi fix, ~(1 << 2) ;[23]
+ nop2 ;[16]
+ nop2 ;[18]
+bit2IsSet:
+ ifrclr phase, USBMINUS ;[20] check phase only if D- changed
+ lpm ;[21]
+ in phase, USBIN ;[22] <- phase (one cycle too late)
+ ori shift, 1 << 2 ;[23]
+bit3AfterSet:
+ st y+, data ;[24]
+entryAfterSet:
+ ifioclr USBIN, USBMINUS ;[26] <--- sample 3
+ rjmp bit3IsClr ;[27]
+ andi shift, ~(7 << 3) ;[28]
+ breq unstuff3s ;[29]
+ in phase, USBIN ;[30] <- phase
+ rjmp bit4AfterSet ;[31]
+unstuff3s:
+ in phase, USBIN ;[31] <- phase (one cycle too late)
+ andi fix, ~(1 << 3) ;[32]
+ nop2 ;[25]
+ nop2 ;[27]
+bit3IsClr:
+ ifrset phase, USBMINUS ;[29] check phase only if D- changed
+ lpm ;[30]
+ in phase, USBIN ;[31] <- phase (one cycle too late)
+ ori shift, 1 << 3 ;[32]
+bit4AfterClr:
+ mov data, fix ;[33] undo this move by swapping defines
+#undef fix
+#define fix x1
+#undef data
+#define data x2
+ ifioset USBIN, USBMINUS ;[34] <--- sample 4
+ rjmp bit4IsSet ;[35]
+ andi shift, ~(7 << 4) ;[36]
+ breq unstuff4c ;[37]
+ in phase, USBIN ;[38] <- phase
+ rjmp bit5AfterClr ;[39]
+unstuff4c:
+ in phase, USBIN ;[39] <- phase (one cycle too late)
+ andi fix, ~(1 << 4) ;[40]
+ nop2 ;[33]
+ nop2 ;[35]
+bit4IsSet:
+ ifrclr phase, USBMINUS ;[37] check phase only if D- changed
+ lpm ;[38]
+ in phase, USBIN ;[39] <- phase (one cycle too late)
+ ori shift, 1 << 4 ;[40]
+bit5AfterSet:
+ ser data ;[41]
+ ifioclr USBIN, USBMINUS ;[42] <--- sample 5
+ rjmp bit5IsClr ;[43]
+ andi shift, ~(7 << 5) ;[44]
+ breq unstuff5s ;[45]
+ in phase, USBIN ;[46] <- phase
+ rjmp bit6AfterSet ;[47]
+unstuff5s:
+ in phase, USBIN ;[47] <- phase (one cycle too late)
+ andi fix, ~(1 << 5) ;[48]
+ nop2 ;[41]
+ nop2 ;[43]
+bit5IsClr:
+ ifrset phase, USBMINUS ;[45] check phase only if D- changed
+ lpm ;[46]
+ in phase, USBIN ;[47] <- phase (one cycle too late)
+ ori shift, 1 << 5 ;[48]
+bit6AfterClr:
+ subi cnt, 1 ;[49]
+ brcs overflow ;[50]
+ ifioset USBIN, USBMINUS ;[51] <--- sample 6
+ rjmp bit6IsSet ;[52]
+ andi shift, ~(3 << 6) ;[53]
+ cpi shift, 2 ;[54]
+ in phase, USBIN ;[55] <- phase
+ brlt unstuff6c ;[56]
+ rjmp bit7AfterClr ;[57]
+unstuff6c:
+ andi fix, ~(1 << 6) ;[50]
+ lpm ;[51]
+bit6IsSet:
+ ifrclr phase, USBMINUS ;[54] check phase only if D- changed
+ lpm ;[55]
+ in phase, USBIN ;[56] <- phase (one cycle too late)
+ ori shift, 1 << 6 ;[57]
+bit7AfterSet:
+ ifioclr USBIN, USBMINUS ;[59] <--- sample 7
+ rjmp bit7IsClr ;[60]
+ andi shift, ~(1 << 7) ;[61]
+ cpi shift, 4 ;[62]
+ in phase, USBIN ;[63] <- phase
+ brlt unstuff7s ;[64]
+ rjmp bit0AfterSet ;[65] -> [00] == [67]
+unstuff7s:
+ andi fix, ~(1 << 7) ;[58]
+ nop ;[59]
+ rjmp bit7IsClr ;[60]
+
+macro POP_STANDARD ; 14 cycles
+ pop r0
+ pop cnt
+ pop x3
+ pop x2
+ pop x1
+ pop shift
+ pop YH
+ endm
+macro POP_RETI ; 5 cycles
+ pop YL
+ out SREG, YL
+ pop YL
+ endm
+
+#include "asmcommon.inc"
+
+;----------------------------------------------------------------------------
+; Transmitting data
+;----------------------------------------------------------------------------
+
+txByteLoop:
+txBitloop:
+stuffN1Delay: ; [03]
+ ror shift ;[-5] [11] [63]
+ brcc doExorN1 ;[-4] [64]
+ subi x3, 1 ;[-3]
+ brne commonN1 ;[-2]
+ lsl shift ;[-1] compensate ror after rjmp stuffDelay
+ nop ;[00] stuffing consists of just waiting 8 cycles
+ rjmp stuffN1Delay ;[01] after ror, C bit is reliably clear
+
+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
+
+; USB spec says:
+; idle = J
+; J = (D+ = 0), (D- = 1) or USBOUT = 0x01
+; K = (D+ = 1), (D- = 0) or USBOUT = 0x02
+; Spec allows 7.5 bit times from EOP to SOP for replies (= 60 cycles)
+
+;usbSend:
+;pointer to data in 'Y'
+;number of bytes in 'cnt' -- including sync byte
+;uses: x1...x3, shift, cnt, Y [x1 = mirror USBOUT, x2 = USBMASK, x3 = bitstuff cnt]
+;Numbers in brackets are time since first bit of sync pattern is sent (start of instruction)
+usbSendAndReti:
+ in x2, USBDDR ;[-10] 10 cycles until SOP
+ ori x2, USBMASK ;[-9]
+ sbi USBOUT, USBMINUS ;[-8] prepare idle state; D+ and D- must have been 0 (no pullups)
+ out USBDDR, x2 ;[-6] <--- acquire bus
+ in x1, USBOUT ;[-5] port mirror for tx loop
+ ldi shift, 0x40 ;[-4] sync byte is first byte sent (we enter loop after ror)
+ ldi x2, USBMASK ;[-3]
+doExorN1:
+ eor x1, x2 ;[-2] [06] [62]
+ ldi x3, 6 ;[-1] [07] [63]
+commonN1:
+stuffN2Delay:
+ out USBOUT, x1 ;[00] [08] [64] <--- set bit
+ ror shift ;[01]
+ brcc doExorN2 ;[02]
+ subi x3, 1 ;[03]
+ brne commonN2 ;[04]
+ lsl shift ;[05] compensate ror after rjmp stuffDelay
+ rjmp stuffN2Delay ;[06] after ror, C bit is reliably clear
+doExorN2:
+ eor x1, x2 ;[04] [12]
+ ldi x3, 6 ;[05] [13]
+commonN2:
+ nop2 ;[06] [14]
+ subi cnt, 171 ;[08] [16] trick: (3 * 171) & 0xff = 1
+ out USBOUT, x1 ;[09] [17] <--- set bit
+ brcs txBitloop ;[10] [27] [44]
+
+stuff6Delay:
+ ror shift ;[45] [53]
+ brcc doExor6 ;[46]
+ subi x3, 1 ;[47]
+ brne common6 ;[48]
+ lsl shift ;[49] compensate ror after rjmp stuffDelay
+ nop ;[50] stuffing consists of just waiting 8 cycles
+ rjmp stuff6Delay ;[51] after ror, C bit is reliably clear
+doExor6:
+ eor x1, x2 ;[48] [56]
+ ldi x3, 6 ;[49]
+common6:
+stuff7Delay:
+ ror shift ;[50] [58]
+ out USBOUT, x1 ;[51] <--- set bit
+ brcc doExor7 ;[52]
+ subi x3, 1 ;[53]
+ brne common7 ;[54]
+ lsl shift ;[55] compensate ror after rjmp stuffDelay
+ rjmp stuff7Delay ;[56] after ror, C bit is reliably clear
+doExor7:
+ eor x1, x2 ;[54] [62]
+ ldi x3, 6 ;[55]
+common7:
+ ld shift, y+ ;[56]
+ nop ;[58]
+ tst cnt ;[59]
+ out USBOUT, x1 ;[60] [00]<--- set bit
+ brne txByteLoop ;[61] [01]
+;make SE0:
+ cbr x1, USBMASK ;[02] prepare SE0 [spec says EOP may be 15 to 18 cycles]
+ lds x2, usbNewDeviceAddr;[03]
+ lsl x2 ;[05] we compare with left shifted address
+ subi YL, 2 + 0 ;[06] Only assign address on data packets, not ACK/NAK in r0
+ sbci YH, 0 ;[07]
+ out USBOUT, x1 ;[00] <-- out SE0 -- from now 2 bits = 16 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
+ breq skipAddrAssign ;[01]
+ sts usbDeviceAddr, x2 ; if not skipped: SE0 is one cycle longer
+skipAddrAssign:
+;end of usbDeviceAddress transfer
+ ldi x2, 1<<USB_INTR_PENDING_BIT;[03] int0 occurred during TX -- clear pending flag
+ USB_STORE_PENDING(x2) ;[04]
+ ori x1, USBIDLE ;[05]
+ in x2, USBDDR ;[06]
+ cbr x2, USBMASK ;[07] set both pins to input
+ mov x3, x1 ;[08]
+ cbr x3, USBMASK ;[09] configure no pullup on both pins
+ lpm ;[10]
+ lpm ;[13]
+ out USBOUT, x1 ;[16] <-- out J (idle) -- end of SE0 (EOP signal)
+ out USBDDR, x2 ;[17] <-- release bus now
+ out USBOUT, x3 ;[18] <-- ensure no pull-up resistors are active
+ rjmp doReturn
+
+
+
+/*****************************************************************************
+The following PHP script generates a code skeleton for the receiver routine:
+
+<?php
+
+function printCmdBuffer($thisBit)
+{
+global $cycle;
+
+ $nextBit = ($thisBit + 1) % 8;
+ $s = ob_get_contents();
+ ob_end_clean();
+ $s = str_replace("#", $thisBit, $s);
+ $s = str_replace("@", $nextBit, $s);
+ $lines = explode("\n", $s);
+ for($i = 0; $i < count($lines); $i++){
+ $s = $lines[$i];
+ if(ereg("\\[([0-9-][0-9])\\]", $s, $regs)){
+ $c = $cycle + (int)$regs[1];
+ $s = ereg_replace("\\[[0-9-][0-9]\\]", sprintf("[%02d]", $c), $s);
+ }
+ if(strlen($s) > 0)
+ echo "$s\n";
+ }
+}
+
+function printBit($isAfterSet, $bitNum)
+{
+ ob_start();
+ if($isAfterSet){
+?>
+ ifioclr USBIN, USBMINUS ;[00] <--- sample
+ rjmp bit#IsClr ;[01]
+ andi shift, ~(7 << #) ;[02]
+ breq unstuff#s ;[03]
+ in phase, USBIN ;[04] <- phase
+ rjmp bit@AfterSet ;[05]
+unstuff#s:
+ in phase, USBIN ;[05] <- phase (one cycle too late)
+ andi fix, ~(1 << #) ;[06]
+ nop2 ;[-1]
+ nop2 ;[01]
+bit#IsClr:
+ ifrset phase, USBMINUS ;[03] check phase only if D- changed
+ lpm ;[04]
+ in phase, USBIN ;[05] <- phase (one cycle too late)
+ ori shift, 1 << # ;[06]
+<?php
+ }else{
+?>
+ ifioset USBIN, USBMINUS ;[00] <--- sample
+ rjmp bit#IsSet ;[01]
+ andi shift, ~(7 << #) ;[02]
+ breq unstuff#c ;[03]
+ in phase, USBIN ;[04] <- phase
+ rjmp bit@AfterClr ;[05]
+unstuff#c:
+ in phase, USBIN ;[05] <- phase (one cycle too late)
+ andi fix, ~(1 << #) ;[06]
+ nop2 ;[-1]
+ nop2 ;[01]
+bit#IsSet:
+ ifrclr phase, USBMINUS ;[03] check phase only if D- changed
+ lpm ;[04]
+ in phase, USBIN ;[05] <- phase (one cycle too late)
+ ori shift, 1 << # ;[06]
+<?php
+ }
+ printCmdBuffer($bitNum);
+}
+
+$bitStartCycles = array(1, 9, 17, 26, 34, 42, 51, 59);
+for($i = 0; $i < 16; $i++){
+ $bit = $i % 8;
+ $emitClrCode = ($i + (int)($i / 8)) % 2;
+ $cycle = $bitStartCycles[$bit];
+ if($emitClrCode){
+ printf("bit%dAfterClr:\n", $bit);
+ }else{
+ printf("bit%dAfterSet:\n", $bit);
+ }
+ ob_start();
+ echo " ***** ;[-1]\n";
+ printCmdBuffer($bit);
+ printBit(!$emitClrCode, $bit);
+ if($i == 7)
+ echo "\n";
+}
+
+?>
+*****************************************************************************/