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/* Name: usbdrvasm165.inc
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* Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers
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* Author: Christian Starkjohann
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* Creation Date: 2007-04-22
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* Tabsize: 4
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* Copyright: (c) 2007 by OBJECTIVE DEVELOPMENT Software GmbH
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* License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt)
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*/
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/* Do not link this file! Link usbdrvasm.S instead, which includes the
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* appropriate implementation!
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*/
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/*
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General Description:
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This file is the 16.5 MHz version of the USB driver. It is intended for the
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ATTiny45 and similar controllers running on 16.5 MHz internal RC oscillator.
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This version contains a phase locked loop in the receiver routine to cope with
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slight clock rate deviations of up to +/- 1%.
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See usbdrv.h for a description of the entire driver.
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Since almost all of this code is timing critical, don't change unless you
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really know what you are doing! Many parts require not only a maximum number
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of CPU cycles, but even an exact number of cycles!
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*/
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;Software-receiver engine. Strict timing! Don't change unless you can preserve timing!
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;interrupt response time: 4 cycles + insn running = 7 max if interrupts always enabled
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;max allowable interrupt latency: 59 cycles -> max 52 cycles interrupt disable
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;max stack usage: [ret(2), r0, SREG, YL, YH, shift, x1, x2, x3, x4, cnt] = 12 bytes
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;nominal frequency: 16.5 MHz -> 11 cycles per bit
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; 16.3125 MHz < F_CPU < 16.6875 MHz (+/- 1.1%)
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; Numbers in brackets are clocks counted from center of last sync bit
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; when instruction starts
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USB_INTR_VECTOR:
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;order of registers pushed: YL, SREG [sofError], r0, YH, shift, x1, x2, x3, x4, cnt
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push YL ;[-23] push only what is necessary to sync with edge ASAP
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in YL, SREG ;[-21]
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push YL ;[-20]
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;----------------------------------------------------------------------------
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; Synchronize with sync pattern:
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;----------------------------------------------------------------------------
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;sync byte (D-) pattern LSb to MSb: 01010100 [1 = idle = J, 0 = K]
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;sync up with J to K edge during sync pattern -- use fastest possible loops
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;The first part waits at most 1 bit long since we must be in sync pattern.
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;YL is guarenteed to be < 0x80 because I flag is clear. When we jump to
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;waitForJ, ensure that this prerequisite is met.
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waitForJ:
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inc YL
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sbis USBIN, USBMINUS
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brne waitForJ ; just make sure we have ANY timeout
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waitForK:
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;The following code results in a sampling window of < 1/4 bit which meets the spec.
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sbis USBIN, USBMINUS ;[-15]
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rjmp foundK ;[-14]
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sbis USBIN, USBMINUS
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rjmp foundK
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sbis USBIN, USBMINUS
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rjmp foundK
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sbis USBIN, USBMINUS
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rjmp foundK
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sbis USBIN, USBMINUS
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rjmp foundK
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sbis USBIN, USBMINUS
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rjmp foundK
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#if USB_COUNT_SOF
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lds YL, usbSofCount
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inc YL
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sts usbSofCount, YL
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#endif /* USB_COUNT_SOF */
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#ifdef USB_SOF_HOOK
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USB_SOF_HOOK
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#endif
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rjmp sofError
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foundK: ;[-12]
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;{3, 5} after falling D- edge, average delay: 4 cycles [we want 5 for center sampling]
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;we have 1 bit time for setup purposes, then sample again. Numbers in brackets
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;are cycles from center of first sync (double K) bit after the instruction
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push r0 ;[-12]
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; [---] ;[-11]
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push YH ;[-10]
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; [---] ;[-9]
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lds YL, usbInputBufOffset;[-8]
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; [---] ;[-7]
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clr YH ;[-6]
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subi YL, lo8(-(usbRxBuf));[-5] [rx loop init]
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sbci YH, hi8(-(usbRxBuf));[-4] [rx loop init]
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mov r0, x2 ;[-3] [rx loop init]
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sbis USBIN, USBMINUS ;[-2] we want two bits K (sample 2 cycles too early)
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rjmp haveTwoBitsK ;[-1]
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pop YH ;[0] undo the pushes from before
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pop r0 ;[2]
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rjmp waitForK ;[4] this was not the end of sync, retry
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; The entire loop from waitForK until rjmp waitForK above must not exceed two
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; bit times (= 22 cycles).
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;----------------------------------------------------------------------------
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; push more registers and initialize values while we sample the first bits:
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;----------------------------------------------------------------------------
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haveTwoBitsK: ;[1]
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push shift ;[1]
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push x1 ;[3]
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push x2 ;[5]
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push x3 ;[7]
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ldi shift, 0xff ;[9] [rx loop init]
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ori x3, 0xff ;[10] [rx loop init] == ser x3, clear zero flag
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in x1, USBIN ;[11] <-- sample bit 0
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bst x1, USBMINUS ;[12]
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bld shift, 0 ;[13]
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push x4 ;[14] == phase
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; [---] ;[15]
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push cnt ;[16]
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; [---] ;[17]
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ldi phase, 0 ;[18] [rx loop init]
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ldi cnt, USB_BUFSIZE;[19] [rx loop init]
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rjmp rxbit1 ;[20]
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; [---] ;[21]
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;----------------------------------------------------------------------------
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; Receiver loop (numbers in brackets are cycles within byte after instr)
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;----------------------------------------------------------------------------
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/*
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byte oriented operations done during loop:
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bit 0: store data
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bit 1: SE0 check
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bit 2: overflow check
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bit 3: catch up
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bit 4: rjmp to achieve conditional jump range
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bit 5: PLL
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bit 6: catch up
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bit 7: jump, fixup bitstuff
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; 87 [+ 2] cycles
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------------------------------------------------------------------
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*/
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continueWithBit5:
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in x2, USBIN ;[055] <-- bit 5
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eor r0, x2 ;[056]
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or phase, r0 ;[057]
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sbrc phase, USBMINUS ;[058]
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lpm ;[059] optional nop3; modifies r0
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in phase, USBIN ;[060] <-- phase
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eor x1, x2 ;[061]
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bst x1, USBMINUS ;[062]
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bld shift, 5 ;[063]
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andi shift, 0x3f ;[064]
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in x1, USBIN ;[065] <-- bit 6
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breq unstuff5 ;[066] *** unstuff escape
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eor phase, x1 ;[067]
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eor x2, x1 ;[068]
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bst x2, USBMINUS ;[069]
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bld shift, 6 ;[070]
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didUnstuff6: ;[ ]
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in r0, USBIN ;[071] <-- phase
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cpi shift, 0x02 ;[072]
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brlo unstuff6 ;[073] *** unstuff escape
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didUnstuff5: ;[ ]
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nop2 ;[074]
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; [---] ;[075]
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in x2, USBIN ;[076] <-- bit 7
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eor x1, x2 ;[077]
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bst x1, USBMINUS ;[078]
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bld shift, 7 ;[079]
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didUnstuff7: ;[ ]
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eor r0, x2 ;[080]
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or phase, r0 ;[081]
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in r0, USBIN ;[082] <-- phase
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cpi shift, 0x04 ;[083]
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brsh rxLoop ;[084]
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; [---] ;[085]
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unstuff7: ;[ ]
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andi x3, ~0x80 ;[085]
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ori shift, 0x80 ;[086]
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in x2, USBIN ;[087] <-- sample stuffed bit 7
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nop ;[088]
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rjmp didUnstuff7 ;[089]
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; [---] ;[090]
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;[080]
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unstuff5: ;[067]
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eor phase, x1 ;[068]
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andi x3, ~0x20 ;[069]
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ori shift, 0x20 ;[070]
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in r0, USBIN ;[071] <-- phase
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mov x2, x1 ;[072]
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nop ;[073]
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nop2 ;[074]
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; [---] ;[075]
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in x1, USBIN ;[076] <-- bit 6
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eor r0, x1 ;[077]
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or phase, r0 ;[078]
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eor x2, x1 ;[079]
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bst x2, USBMINUS ;[080]
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bld shift, 6 ;[081] no need to check bitstuffing, we just had one
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in r0, USBIN ;[082] <-- phase
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rjmp didUnstuff5 ;[083]
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; [---] ;[084]
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;[074]
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unstuff6: ;[074]
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andi x3, ~0x40 ;[075]
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in x1, USBIN ;[076] <-- bit 6 again
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ori shift, 0x40 ;[077]
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nop2 ;[078]
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; [---] ;[079]
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rjmp didUnstuff6 ;[080]
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; [---] ;[081]
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;[071]
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unstuff0: ;[013]
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eor r0, x2 ;[014]
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or phase, r0 ;[015]
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andi x2, USBMASK ;[016] check for SE0
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in r0, USBIN ;[017] <-- phase
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breq didUnstuff0 ;[018] direct jump to se0 would be too long
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andi x3, ~0x01 ;[019]
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ori shift, 0x01 ;[020]
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mov x1, x2 ;[021] mov existing sample
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in x2, USBIN ;[022] <-- bit 1 again
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rjmp didUnstuff0 ;[023]
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; [---] ;[024]
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;[014]
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unstuff1: ;[024]
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eor r0, x1 ;[025]
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or phase, r0 ;[026]
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andi x3, ~0x02 ;[027]
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in r0, USBIN ;[028] <-- phase
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ori shift, 0x02 ;[029]
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mov x2, x1 ;[030]
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rjmp didUnstuff1 ;[031]
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; [---] ;[032]
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;[022]
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unstuff2: ;[035]
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eor r0, x2 ;[036]
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or phase, r0 ;[037]
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andi x3, ~0x04 ;[038]
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in r0, USBIN ;[039] <-- phase
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ori shift, 0x04 ;[040]
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mov x1, x2 ;[041]
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rjmp didUnstuff2 ;[042]
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; [---] ;[043]
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;[033]
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unstuff3: ;[043]
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in x2, USBIN ;[044] <-- bit 3 again
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eor r0, x2 ;[045]
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or phase, r0 ;[046]
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andi x3, ~0x08 ;[047]
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ori shift, 0x08 ;[048]
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nop ;[049]
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in r0, USBIN ;[050] <-- phase
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rjmp didUnstuff3 ;[051]
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; [---] ;[052]
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;[042]
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unstuff4: ;[053]
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andi x3, ~0x10 ;[054]
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in x1, USBIN ;[055] <-- bit 4 again
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ori shift, 0x10 ;[056]
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rjmp didUnstuff4 ;[057]
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; [---] ;[058]
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;[048]
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rxLoop: ;[085]
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eor x3, shift ;[086] reconstruct: x3 is 0 at bit locations we changed, 1 at others
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in x1, USBIN ;[000] <-- bit 0
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st y+, x3 ;[001]
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; [---] ;[002]
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eor r0, x1 ;[003]
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or phase, r0 ;[004]
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eor x2, x1 ;[005]
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in r0, USBIN ;[006] <-- phase
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ser x3 ;[007]
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bst x2, USBMINUS ;[008]
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bld shift, 0 ;[009]
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andi shift, 0xf9 ;[010]
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rxbit1: ;[ ]
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in x2, USBIN ;[011] <-- bit 1
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breq unstuff0 ;[012] *** unstuff escape
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andi x2, USBMASK ;[013] SE0 check for bit 1
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didUnstuff0: ;[ ] Z only set if we detected SE0 in bitstuff
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breq se0 ;[014]
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eor r0, x2 ;[015]
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or phase, r0 ;[016]
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in r0, USBIN ;[017] <-- phase
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eor x1, x2 ;[018]
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bst x1, USBMINUS ;[019]
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bld shift, 1 ;[020]
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andi shift, 0xf3 ;[021]
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didUnstuff1: ;[ ]
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in x1, USBIN ;[022] <-- bit 2
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breq unstuff1 ;[023] *** unstuff escape
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eor r0, x1 ;[024]
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or phase, r0 ;[025]
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subi cnt, 1 ;[026] overflow check
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brcs overflow ;[027]
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in r0, USBIN ;[028] <-- phase
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eor x2, x1 ;[029]
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bst x2, USBMINUS ;[030]
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bld shift, 2 ;[031]
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andi shift, 0xe7 ;[032]
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didUnstuff2: ;[ ]
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in x2, USBIN ;[033] <-- bit 3
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breq unstuff2 ;[034] *** unstuff escape
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310 |
eor r0, x2 ;[035]
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or phase, r0 ;[036]
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312 |
eor x1, x2 ;[037]
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313 |
bst x1, USBMINUS ;[038]
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in r0, USBIN ;[039] <-- phase
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bld shift, 3 ;[040]
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andi shift, 0xcf ;[041]
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didUnstuff3: ;[ ]
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318 |
breq unstuff3 ;[042] *** unstuff escape
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nop ;[043]
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in x1, USBIN ;[044] <-- bit 4
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321 |
eor x2, x1 ;[045]
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322 |
bst x2, USBMINUS ;[046]
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bld shift, 4 ;[047]
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324 |
didUnstuff4: ;[ ]
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325 |
eor r0, x1 ;[048]
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326 |
or phase, r0 ;[049]
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in r0, USBIN ;[050] <-- phase
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328 |
andi shift, 0x9f ;[051]
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329 |
breq unstuff4 ;[052] *** unstuff escape
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330 |
rjmp continueWithBit5;[053]
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331 |
; [---] ;[054]
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332 |
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333 |
macro POP_STANDARD ; 16 cycles
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334 |
pop cnt
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335 |
pop x4
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336 |
pop x3
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337 |
pop x2
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338 |
pop x1
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339 |
pop shift
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340 |
pop YH
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341 |
pop r0
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342 |
endm
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343 |
macro POP_RETI ; 5 cycles
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344 |
pop YL
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345 |
out SREG, YL
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346 |
pop YL
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347 |
endm
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348 |
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349 |
#include "asmcommon.inc"
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350 |
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351 |
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352 |
; USB spec says:
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353 |
; idle = J
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354 |
; J = (D+ = 0), (D- = 1)
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355 |
; K = (D+ = 1), (D- = 0)
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356 |
; Spec allows 7.5 bit times from EOP to SOP for replies
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357 |
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358 |
bitstuff7:
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359 |
eor x1, x4 ;[4]
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360 |
ldi x2, 0 ;[5]
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361 |
nop2 ;[6] C is zero (brcc)
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362 |
rjmp didStuff7 ;[8]
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363 |
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364 |
bitstuffN:
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365 |
eor x1, x4 ;[5]
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366 |
ldi x2, 0 ;[6]
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367 |
lpm ;[7] 3 cycle NOP, modifies r0
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|
368 |
out USBOUT, x1 ;[10] <-- out
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|
369 |
rjmp didStuffN ;[0]
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370 |
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|
371 |
#define bitStatus x3
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372 |
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373 |
sendNakAndReti:
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374 |
ldi cnt, USBPID_NAK ;[-19]
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|
375 |
rjmp sendCntAndReti ;[-18]
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|
376 |
sendAckAndReti:
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|
377 |
ldi cnt, USBPID_ACK ;[-17]
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|
378 |
sendCntAndReti:
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|
379 |
mov r0, cnt ;[-16]
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|
380 |
ldi YL, 0 ;[-15] R0 address is 0
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|
381 |
ldi YH, 0 ;[-14]
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|
382 |
ldi cnt, 2 ;[-13]
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383 |
; rjmp usbSendAndReti fallthrough
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|
384 |
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|
385 |
;usbSend:
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|
386 |
;pointer to data in 'Y'
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|
387 |
;number of bytes in 'cnt' -- including sync byte [range 2 ... 12]
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|
388 |
;uses: x1...x4, shift, cnt, Y
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|
389 |
;Numbers in brackets are time since first bit of sync pattern is sent
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|
390 |
usbSendAndReti: ; 12 cycles until SOP
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|
391 |
in x2, USBDDR ;[-12]
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|
392 |
ori x2, USBMASK ;[-11]
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|
393 |
sbi USBOUT, USBMINUS;[-10] prepare idle state; D+ and D- must have been 0 (no pullups)
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|
394 |
in x1, USBOUT ;[-8] port mirror for tx loop
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|
395 |
out USBDDR, x2 ;[-7] <- acquire bus
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|
396 |
; need not init x2 (bitstuff history) because sync starts with 0
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|
397 |
ldi x4, USBMASK ;[-6] exor mask
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|
398 |
ldi shift, 0x80 ;[-5] sync byte is first byte sent
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|
399 |
ldi bitStatus, 0xff ;[-4] init bit loop counter, works for up to 12 bytes
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|
400 |
byteloop:
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|
401 |
bitloop:
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|
402 |
sbrs shift, 0 ;[8] [-3]
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|
403 |
eor x1, x4 ;[9] [-2]
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|
404 |
out USBOUT, x1 ;[10] [-1] <-- out
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|
405 |
ror shift ;[0]
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|
406 |
ror x2 ;[1]
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|
407 |
didStuffN:
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|
408 |
cpi x2, 0xfc ;[2]
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|
409 |
brcc bitstuffN ;[3]
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|
410 |
nop ;[4]
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|
411 |
subi bitStatus, 37 ;[5] 256 / 7 ~=~ 37
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|
412 |
brcc bitloop ;[6] when we leave the loop, bitStatus has almost the initial value
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|
413 |
sbrs shift, 0 ;[7]
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|
414 |
eor x1, x4 ;[8]
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|
415 |
ror shift ;[9]
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|
416 |
didStuff7:
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|
417 |
out USBOUT, x1 ;[10] <-- out
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|
418 |
ror x2 ;[0]
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|
419 |
cpi x2, 0xfc ;[1]
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|
420 |
brcc bitstuff7 ;[2]
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|
421 |
ld shift, y+ ;[3]
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|
422 |
dec cnt ;[5]
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|
423 |
brne byteloop ;[6]
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|
424 |
;make SE0:
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|
|
425 |
cbr x1, USBMASK ;[7] prepare SE0 [spec says EOP may be 21 to 25 cycles]
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|
426 |
lds x2, usbNewDeviceAddr;[8]
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|
|
427 |
lsl x2 ;[10] we compare with left shifted address
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|
428 |
out USBOUT, x1 ;[11] <-- out SE0 -- from now 2 bits = 22 cycles until bus idle
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|
429 |
;2006-03-06: moved transfer of new address to usbDeviceAddr from C-Code to asm:
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|
430 |
;set address only after data packet was sent, not after handshake
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|
431 |
subi YL, 2 ;[0] Only assign address on data packets, not ACK/NAK in r0
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|
432 |
sbci YH, 0 ;[1]
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|
433 |
breq skipAddrAssign ;[2]
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|
434 |
sts usbDeviceAddr, x2; if not skipped: SE0 is one cycle longer
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|
435 |
skipAddrAssign:
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|
436 |
;end of usbDeviceAddress transfer
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|
437 |
ldi x2, 1<<USB_INTR_PENDING_BIT;[4] int0 occurred during TX -- clear pending flag
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|
438 |
USB_STORE_PENDING(x2) ;[5]
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|
439 |
ori x1, USBIDLE ;[6]
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|
440 |
in x2, USBDDR ;[7]
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|
441 |
cbr x2, USBMASK ;[8] set both pins to input
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|
442 |
mov x3, x1 ;[9]
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|
|
443 |
cbr x3, USBMASK ;[10] configure no pullup on both pins
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|
|
444 |
ldi x4, 4 ;[11]
|
|
|
445 |
se0Delay:
|
|
|
446 |
dec x4 ;[12] [15] [18] [21]
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|
|
447 |
brne se0Delay ;[13] [16] [19] [22]
|
|
|
448 |
out USBOUT, x1 ;[23] <-- out J (idle) -- end of SE0 (EOP signal)
|
|
|
449 |
out USBDDR, x2 ;[24] <-- release bus now
|
|
|
450 |
out USBOUT, x3 ;[25] <-- ensure no pull-up resistors are active
|
|
|
451 |
rjmp doReturn
|
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|
452 |
|