-
-SIG_INTERRUPT0:
-;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: 32 cycles -> max 25 cycles interrupt disable
-;max stack usage: [ret(2), x1, SREG, x2, cnt, shift, YH, YL, x3, x4] = 11 bytes
-usbInterrupt:
-;order of registers pushed:
-;x1, SREG, x2, cnt, shift, [YH, YL, x3]
- push x1 ;2 push only what is necessary to sync with edge ASAP
- in x1, SREG ;1
- push x1 ;2
-;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)
-#if !USB_CFG_SAMPLE_EXACT
- ldi x1, 5 ;1 setup a timeout for waitForK
-#endif
-waitForJ:
- sbis USBIN, USBMINUS ;1 wait for D- == 1
- rjmp waitForJ ;2
-#if USB_CFG_SAMPLE_EXACT
-;The following code represents the unrolled loop in the else branch. It
-;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
- nop
- nop2
-foundK:
-#else
-waitForK:
- dec x1 ;1
- sbic USBIN, USBMINUS ;1 wait for D- == 0
- brne waitForK ;2
-#endif
-;{2, 6} 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:
- push x2 ;2
- push cnt ;2
- push shift ;2
-shortcutEntry:
- ldi cnt, 1 ;1 pre-init bit counter (-1 because no dec follows, -1 because 1 bit already sampled)
- ldi x2, 1<<USB_CFG_DPLUS_BIT ;1 -> 8 edge sync ended with D- == 0
-;now wait until SYNC byte is over. Wait for either 2 bits low (success) or 2 bits high (failure)
-waitNoChange:
- in x1, USBIN ;1 <-- sample, timing: edge + {2, 6} cycles
- eor x2, x1 ;1
- sbrc x2, USBMINUS ;1 | 2
- ldi cnt, 2 ;1 | 0 cnt = numBits - 1 (because dec follows)
- mov x2, x1 ;1
- dec cnt ;1
- brne waitNoChange ;2 | 1
- sbrc x1, USBMINUS ;2
- rjmp sofError ;0 two consecutive "1" bits -> framing error
-;start reading data, but don't check for bitstuffing because these are the
-;first bits. Use the cycles for initialization instead. Note that we read and
-;store the binary complement of the data stream because eor results in 1 for
-;a change and 0 for no change.
- in x1, USBIN ;1 <-- sample bit 0, timing: edge + {3, 7} cycles
- eor x2, x1 ;1
- ldi shift, 0x00 ;1 prepare for bitstuff check later on in loop
- bst x2, USBMINUS ;1
- bld shift, 0 ;1
- push YH ;2 -> 7
- in x2, USBIN ;1 <-- sample bit 1, timing: edge + {2, 6} cycles
- eor x1, x2 ;1
- bst x1, USBMINUS ;1
- bld shift, 1 ;1
- push YL ;2
- lds YL, usbInputBuf ;2 -> 8
- in x1, USBIN ;1 <-- sample bit 2, timing: edge + {2, 6} cycles
- eor x2, x1 ;1
- bst x2, USBMINUS ;1
- bld shift, 2 ;1
- ldi cnt, USB_BUFSIZE;1
- ldi YH, hi8(usbRxBuf);1 assume that usbRxBuf does not cross a page
- push x3 ;2 -> 8
- in x2, USBIN ;1 <-- sample bit 3, timing: edge + {2, 6} cycles
- eor x1, x2 ;1
- bst x1, USBMINUS ;1
- bld shift, 3 ;1
- ser x3 ;1
- nop ;1
- rjmp rxbit4 ;2 -> 8
-
-shortcutToStart: ;{,43} into next frame: max 5.5 sync bits missed
-#if !USB_CFG_SAMPLE_EXACT
- ldi x1, 5 ;2 setup timeout
-#endif
-waitForJ1:
- sbis USBIN, USBMINUS ;1 wait for D- == 1
- rjmp waitForJ1 ;2
-#if USB_CFG_SAMPLE_EXACT
-;The following code represents the unrolled loop in the else branch. It
-;results in a sampling window of 1/4 bit which meets the spec.
- sbis USBIN, USBMINUS
- rjmp foundK1
- sbis USBIN, USBMINUS
- rjmp foundK1
- sbis USBIN, USBMINUS
- rjmp foundK1
- nop
- nop2
-foundK1:
-#else
-waitForK1:
- dec x1 ;1
- sbic USBIN, USBMINUS ;1 wait for D- == 0
- brne waitForK1 ;2
-#endif
- pop YH ;2 correct stack alignment
- nop2 ;2 delay for the same time as the pushes in the original code
- rjmp shortcutEntry ;2
-
-; ################# receiver loop #################
-; extra jobs done during bit interval:
-; bit 6: se0 check
-; bit 7: or, store, clear
-; bit 0: recover from delay [SE0 is unreliable here due to bit dribbling in hubs]
-; bit 1: se0 check
-; bit 2: se0 check
-; bit 3: overflow check
-; bit 4: se0 check
-; bit 5: rjmp
-
-; stuffed* helpers have the functionality of a subroutine, but we can't afford
-; the overhead of a call. We therefore need a separate routine for each caller
-; which jumps back appropriately.
-
-stuffed5: ;1 for branch taken
- in x2, USBIN ;1 <-- sample @ +1
- andi x2, USBMASK ;1
- breq se0a ;1
- andi x3, ~0x20 ;1
- ori shift, 0x20 ;1
- rjmp rxbit6 ;2
-
-stuffed6: ;1 for branch taken
- in x1, USBIN ;1 <-- sample @ +1
- andi x1, USBMASK ;1
- breq se0a ;1
- andi x3, ~0x40 ;1
- ori shift, 0x40 ;1
- rjmp rxbit7 ;2
-
-; This is somewhat special because it has to compensate for the delay in bit 7
-stuffed7: ;1 for branch taken
- andi x1, USBMASK ;1 already sampled by caller
- breq se0a ;1
- mov x2, x1 ;1 ensure correct NRZI sequence
- ori shift, 0x80 ;1 no need to set reconstruction in x3: shift has already been used
- in x1, USBIN ;1 <-- sample bit 0
- rjmp unstuffed7 ;2
-
-stuffed0: ;1 for branch taken
- in x1, USBIN ;1 <-- sample @ +1
- andi x1, USBMASK ;1
- breq se0a ;1
- andi x3, ~0x01 ;1
- ori shift, 0x01 ;1
- rjmp rxbit1 ;2
-
-;-----------------------------
-rxLoop:
- breq stuffed5 ;1
-rxbit6:
- in x1, USBIN ;1 <-- sample bit 6
- andi x1, USBMASK ;1
- breq se0a ;1
- eor x2, x1 ;1
- bst x2, USBMINUS;1
- bld shift, 6 ;1
- cpi shift, 0x02 ;1
- brlo stuffed6 ;1
-rxbit7:
- in x2, USBIN ;1 <-- sample bit 7
- eor x1, x2 ;1
- bst x1, USBMINUS;1
- bld shift, 7 ;1
- eor x3, shift ;1 x3 is 0 at bit locations we changed, 1 at others
- st y+, x3 ;2 the eor above reconstructed modified bits and inverted rx data
- ser x3 ;1
-rxbit0:
- in x1, USBIN ;1 <-- sample bit 0
- cpi shift, 0x04 ;1
- brlo stuffed7 ;1
-unstuffed7:
- eor x2, x1 ;1
- bst x2, USBMINUS;1
- bld shift, 0 ;1
- andi shift, 0xf9 ;1
- breq stuffed0 ;1
-rxbit1:
- in x2, USBIN ;1 <-- sample bit 1
- andi x2, USBMASK ;1
-se0a: ; enlarge jump range to SE0
- breq se0 ;1 check for SE0 more often close to start of byte
- eor x1, x2 ;1
- bst x1, USBMINUS;1
- bld shift, 1 ;1
- andi shift, 0xf3 ;1
- breq stuffed1 ;1
-rxbit2:
- in x1, USBIN ;1 <-- sample bit 2
- andi x1, USBMASK ;1
- breq se0 ;1
- eor x2, x1 ;1
- bst x2, USBMINUS;1
- bld shift, 2 ;1
- andi shift, 0xe7 ;1
- breq stuffed2 ;1
-rxbit3:
- in x2, USBIN ;1 <-- sample bit 3
- eor x1, x2 ;1
- bst x1, USBMINUS;1
- bld shift, 3 ;1
- dec cnt ;1 check for buffer overflow
- breq overflow ;1
- andi shift, 0xcf ;1
- breq stuffed3 ;1
-rxbit4:
- in x1, USBIN ;1 <-- sample bit 4
- andi x1, USBMASK ;1
- breq se0 ;1
- eor x2, x1 ;1
- bst x2, USBMINUS;1
- bld shift, 4 ;1
- andi shift, 0x9f ;1
- breq stuffed4 ;1
-rxbit5:
- in x2, USBIN ;1 <-- sample bit 5
- eor x1, x2 ;1
- bst x1, USBMINUS;1
- bld shift, 5 ;1
- andi shift, 0x3f ;1
- rjmp rxLoop ;2
-;-----------------------------
-
-stuffed1: ;1 for branch taken
- in x2, USBIN ;1 <-- sample @ +1
- andi x2, USBMASK ;1
- breq se0 ;1
- andi x3, ~0x02 ;1
- ori shift, 0x02 ;1
- rjmp rxbit2 ;2
-
-stuffed2: ;1 for branch taken
- in x1, USBIN ;1 <-- sample @ +1
- andi x1, USBMASK ;1
- breq se0 ;1
- andi x3, ~0x04 ;1
- ori shift, 0x04 ;1
- rjmp rxbit3 ;2
-
-stuffed3: ;1 for branch taken
- in x2, USBIN ;1 <-- sample @ +1
- andi x2, USBMASK ;1
- breq se0 ;1
- andi x3, ~0x08 ;1
- ori shift, 0x08 ;1
- rjmp rxbit4 ;2
-
-stuffed4: ;1 for branch taken
- in x1, USBIN ;1 <-- sample @ +1
- andi x1, USBMASK ;1
- breq se0 ;1
- andi x3, ~0x10 ;1
- ori shift, 0x10 ;1
- rjmp rxbit5 ;2
-
-;################ end receiver loop ###############
-
-overflow: ; ignore package if buffer overflow
- rjmp rxDoReturn ; enlarge jump range
-
-;This is the only non-error exit point for the software receiver loop
-;{4, 20} cycles after start of SE0, typically {10, 18} after SE0 start = {-6, 2} from end of SE0
-;next sync starts {16,} cycles after SE0 -> worst case start: +4 from next sync start
-;we don't check any CRCs here because there is no time left.
-se0: ;{-6, 2} from end of SE0 / {,4} into next frame
- mov cnt, YL ;1 assume buffer in lower 256 bytes of memory
- lds YL, usbInputBuf ;2 reposition to buffer start
- sub cnt, YL ;1 length of message
- ldi x1, 1<<USB_INTR_PENDING_BIT ;1
- cpi cnt, 3 ;1
- out USB_INTR_PENDING, x1;1 clear pending intr and check flag later. SE0 must be over. {,10} into next frame
- brlo rxDoReturn ;1 ensure valid packet size, ignore others
- ld x1, y ;2 PID
- ldd x2, y+1 ;2 ADDR + 1 bit endpoint number
- mov x3, x2 ;1 store for endpoint number
- andi x2, 0x7f ;1 mask endpoint number bit
- lds shift, usbDeviceAddr;2
- cpi x1, USBPID_SETUP ;1
- breq isSetupOrOut ;2 -> 19 = {13, 21} from SE0 end
- cpi x1, USBPID_OUT ;1
- breq isSetupOrOut ;2 -> 22 = {16, 24} from SE0 end / {,24} into next frame
- cpi x1, USBPID_IN ;1
- breq handleIn ;1
-#define USB_DATA_MASK ~(USBPID_DATA0 ^ USBPID_DATA1)
- andi x1, USB_DATA_MASK ;1
- cpi x1, USBPID_DATA0 & USB_DATA_MASK ;1
- brne rxDoReturn ;1 not a data PID -- ignore
-isData:
- lds x2, usbCurrentTok ;2
- tst x2 ;1
- breq rxDoReturn ;1 for other device or spontaneous data -- ignore
- lds x1, usbRxLen ;2
- cpi x1, 0 ;1
- brne sendNakAndReti ;1 no buffer space available / {30, 38} from SE0 end
-; 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 ;1 zero sized data packets are status phase only -- ignore and ack
- brmi sendAckAndReti ;1 keep rx buffer clean -- we must not NAK next SETUP
- sts usbRxLen, cnt ;2 store received data, swap buffers
- sts usbRxToken, x2 ;2
- lds x1, usbAppBuf ;2
- sts usbAppBuf, YL ;2
- sts usbInputBuf, x1 ;2 buffers now swapped
- rjmp sendAckAndReti ;2 -> {43, 51} from SE0 end
-
-handleIn: ; {18, 26} from SE0 end
- cp x2, shift ;1 shift contains our device addr
- brne rxDoReturn ;1 other device
-#if USB_CFG_HAVE_INTRIN_ENDPOINT
- sbrc x3, 7 ;2 x3 contains addr + endpoint
- rjmp handleIn1 ;0
-#endif
- lds cnt, usbTxLen ;2
- sbrc cnt, 4 ;2
- rjmp sendCntAndReti ;0 -> {27, 35} from SE0 end
- ldi x1, USBPID_NAK ;1
- sts usbTxLen, x1 ;2 buffer is now free
- ldi YL, lo8(usbTxBuf) ;1
- ldi YH, hi8(usbTxBuf) ;1
- rjmp usbSendAndReti ;2 -> {34, 43} from SE0 end
-
-; 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.
-
-otherOutOrSetup:
- clr x1
- sts usbCurrentTok, x1
-rxDoReturn:
- pop x3 ;2
- pop YL ;2
- pop YH ;2
- rjmp sofError ;2
-
-isSetupOrOut: ; we must be fast here -- a data package may follow / {,24} into next frame
- cp x2, shift ;1 shift contains our device addr
- brne otherOutOrSetup ;1 other device -- ignore
-#if USB_CFG_IMPLEMENT_FN_WRITEOUT /* if we need second OUT endpoint, store endpoint address */
- andi x1, 0x7f ;1 mask out MSb in token
- andi x3, 0x80 ;1 mask out all but endpoint address
- or x1, x3 ;1 merge endpoint into currentToken
- sts usbCurrentTok, x1 ;2
- brmi dontResetEP0 ;1 endpoint 1 -> don't reset endpoint 0 input
-#else
- sts usbCurrentTok, x1 ;2
-#endif
-;A transmission can still have data in the output buffer while we receive a
-;SETUP package with an IN phase. To avoid that the old data is sent as a reply,
-;we abort transmission. We don't need to reset usbMsgLen because it is used
-;from the main loop only where the setup is processed anyway.
- ldi x1, USBPID_NAK ;1
- sts usbTxLen, x1 ;2 abort transmission
-dontResetEP0:
- pop x3 ;2
- pop YL ;2
- in x1, USB_INTR_PENDING;1
- sbrc x1, USB_INTR_PENDING_BIT;1 check whether data is already arriving {,41} into next frame
- rjmp shortcutToStart ;2 save the pops and pushes -- a new interrupt is aready pending
-;If the jump above was not taken, we can be at {,2} into the next frame here
- pop YH ;2
-txDoReturn:
-sofError: ; error in start of frame -- ignore frame
- ldi x1, 1<<USB_INTR_PENDING_BIT;1 many int0 events occurred during our processing -- clear pending flag
- out USB_INTR_PENDING, x1;1
- pop shift ;2
- pop cnt ;2
- pop x2 ;2
- pop x1 ;2
- out SREG, x1 ;1
- pop x1 ;2
- reti ;4 -> {,21} into next frame -> up to 3 sync bits missed
-
-sendCntAndReti: ; 19 cycles until SOP
- mov x3, cnt ;1
- rjmp usbSendX3 ;2
-sendNakAndReti: ; 19 cycles until SOP
- ldi x3, USBPID_NAK ;1
- rjmp usbSendX3 ;2
-sendAckAndReti: ; 17 cycles until SOP
- ldi x3, USBPID_ACK ;1
-usbSendX3:
- ldi YL, 20 ;1 'x3' is R20
- ldi YH, 0 ;1
- ldi cnt, 2 ;1
-;;;;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...x4, shift, cnt, Y
-usbSendAndReti: ; SOP starts 13 cycles after call
- push x4 ;2
- ldi x4, USBMASK ;1 exor mask
- sbi USBOUT, USBMINUS;1 prepare idle state; D+ and D- must have been 0 (no pullups)
- in x1, USBOUT ;1 port mirror for tx loop
- sbi USBDDR, USBMINUS;1
- sbi USBDDR, USBPLUS ;1 set D+ and D- to output: acquire bus
-; need not init x2 (bitstuff history) because sync starts with 0
- ldi shift, 0x80 ;1 sync byte is first byte sent
- rjmp txLoop ;2 -> 13 + 3 = 16 cycles until SOP
-
-#if USB_CFG_HAVE_INTRIN_ENDPOINT /* placed here due to relative jump range */
-handleIn1: ;{23, 31} from SE0
- ldi x1, USBPID_NAK ;1
-#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 ;2
- sbrc x2, 0 ;2 1
- rjmp handleIn3 ;0 2
-#endif
- lds cnt, usbTxLen1 ;2
- sbrc cnt, 4 ;2
- rjmp sendCntAndReti ;0
- sts usbTxLen1, x1 ;2
- ldi YL, lo8(usbTxBuf1);1
- ldi YH, hi8(usbTxBuf1);1
- rjmp usbSendAndReti ;2 -> arrives at usbSendAndReti {34, 42} from SE0
-
-#if USB_CFG_HAVE_INTRIN_ENDPOINT3
-handleIn3:
- lds cnt, usbTxLen3 ;2
- sbrc cnt, 4 ;2
- rjmp sendCntAndReti ;0
- sts usbTxLen3, x1 ;2
- ldi YL, lo8(usbTxBuf3);1
- ldi YH, hi8(usbTxBuf3);1
- rjmp usbSendAndReti ;2 -> arrives at usbSendAndReti {39, 47} from SE0
-#endif
-#endif
-
-bitstuff0: ;1 (for branch taken)
- eor x1, x4 ;1
- ldi x2, 0 ;1
- out USBOUT, x1 ;1 <-- out
- rjmp didStuff0 ;2 branch back 2 cycles earlier
-bitstuff1: ;1 (for branch taken)
- eor x1, x4 ;1
- ldi x2, 0 ;1
- sec ;1 set carry so that brsh will not jump
- out USBOUT, x1 ;1 <-- out
- rjmp didStuff1 ;2 jump back 1 cycle earler
-bitstuff2: ;1 (for branch taken)
- eor x1, x4 ;1
- ldi x2, 0 ;1
- rjmp didStuff2 ;2 jump back 3 cycles earlier and do out
-bitstuff3: ;1 (for branch taken)
- eor x1, x4 ;1
- ldi x2, 0 ;1
- rjmp didStuff3 ;2 jump back earlier
-
-txLoop:
- sbrs shift, 0 ;1
- eor x1, x4 ;1
- out USBOUT, x1 ;1 <-- out
- ror shift ;1
- ror x2 ;1
-didStuff0:
- cpi x2, 0xfc ;1
- brsh bitstuff0 ;1
- sbrs shift, 0 ;1
- eor x1, x4 ;1
- ror shift ;1
- out USBOUT, x1 ;1 <-- out
- ror x2 ;1
- cpi x2, 0xfc ;1
-didStuff1:
- brsh bitstuff1 ;1
- sbrs shift, 0 ;1
- eor x1, x4 ;1
- ror shift ;1
- ror x2 ;1
-didStuff2:
- out USBOUT, x1 ;1 <-- out
- cpi x2, 0xfc ;1
- brsh bitstuff2 ;1
- sbrs shift, 0 ;1
- eor x1, x4 ;1
- ror shift ;1
- ror x2 ;1
-didStuff3:
- cpi x2, 0xfc ;1
- out USBOUT, x1 ;1 <-- out
- brsh bitstuff3 ;1
- nop2 ;2
- ld x3, y+ ;2
- sbrs shift, 0 ;1
- eor x1, x4 ;1
- out USBOUT, x1 ;1 <-- out
- ror shift ;1
- ror x2 ;1
-didStuff4:
- cpi x2, 0xfc ;1
- brsh bitstuff4 ;1
- sbrs shift, 0 ;1
- eor x1, x4 ;1
- ror shift ;1
- out USBOUT, x1 ;1 <-- out
- ror x2 ;1
- cpi x2, 0xfc ;1
-didStuff5:
- brsh bitstuff5 ;1
- sbrs shift, 0 ;1
- eor x1, x4 ;1
- ror shift ;1
- ror x2 ;1
-didStuff6:
- out USBOUT, x1 ;1 <-- out
- cpi x2, 0xfc ;1
- brsh bitstuff6 ;1
- sbrs shift, 0 ;1
- eor x1, x4 ;1
- ror shift ;1
- ror x2 ;1
-didStuff7:
- cpi x2, 0xfc ;1
- out USBOUT, x1 ;1 <-- out
- brsh bitstuff7 ;1
- mov shift, x3 ;1
- dec cnt ;1
- brne txLoop ;2 | 1
- cbr x1, USBMASK ;1 prepare SE0 [spec says EOP may be 15 to 18 cycles]
- pop x4 ;2
- out USBOUT, x1 ;1 <-- out SE0 -- from now 2 bits = 16 cycles until bus idle
- ldi cnt, 2 ;| takes cnt * 3 cycles
-se0Delay: ;|
- dec cnt ;|
- brne se0Delay ;| -> 2 * 3 = 6 cycles
-;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
- lds x2, usbNewDeviceAddr;2
- subi YL, 20 + 2 ;1
- sbci YH, 0 ;1
- breq skipAddrAssign ;2
- sts usbDeviceAddr, x2 ;0 if not skipped: SE0 is one cycle longer
-skipAddrAssign:
-;end of usbDeviceAddress transfer
- ori x1, USBIDLE ;1
- in x2, USBDDR ;1
- cbr x2, USBMASK ;1 set both pins to input
- out USBOUT, x1 ;1 <-- out J (idle) -- end of SE0 (EOP signal)
- cbr x1, USBMASK ;1 configure no pullup on both pins
- pop x3 ;2
- pop YL ;2
- out USBDDR, x2 ;1 <-- release bus now
- out USBOUT, x1 ;1 set pullup state
- pop YH ;2
- rjmp txDoReturn ;2 [we want to jump to rxDoReturn, but this saves cycles]
-
-
-bitstuff4: ;1 (for branch taken)
- eor x1, x4 ;1
- ldi x2, 0 ;1
- out USBOUT, x1 ;1 <-- out
- rjmp didStuff4 ;2 jump back 2 cycles earlier
-bitstuff5: ;1 (for branch taken)
- eor x1, x4 ;1
- ldi x2, 0 ;1
- sec ;1 set carry so that brsh is not taken
- out USBOUT, x1 ;1 <-- out
- rjmp didStuff5 ;2 jump back 1 cycle earlier
-bitstuff6: ;1 (for branch taken)
- eor x1, x4 ;1
- ldi x2, 0 ;1
- rjmp didStuff6 ;2 jump back 3 cycles earlier and do out there
-bitstuff7: ;1 (for branch taken)
- eor x1, x4 ;1
- ldi x2, 0 ;1
- rjmp didStuff7 ;2 jump back 4 cycles earlier
-
-; ######################## utility functions ########################
projects / pub / USBasp.git / blobdiff