usbdrv/usbdrvasm12.inc@16e4becf8b1b
usbdrv/usbdrvasm12.inc
Fri, 17 Feb 2017 13:40:27 +0100
- author
- mbayer
- date
- Fri, 17 Feb 2017 13:40:27 +0100
- changeset 7
- 16e4becf8b1b
- parent 0
- 9e9b2c78bd31
- permissions
- -rw-r--r--
final pics
/* Name: usbdrvasm12.inc * Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers * Author: Christian Starkjohann * Creation Date: 2004-12-29 * Tabsize: 4 * Copyright: (c) 2007 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 MHz version of the asssembler part of the USB driver. It requires a 12 MHz crystal (not a ceramic resonator and not a calibrated RC oscillator). 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! Timing constraints according to spec (in bit times): timing subject min max CPUcycles --------------------------------------------------------------------------- EOP of OUT/SETUP to sync pattern of DATA0 (both rx) 2 16 16-128 EOP of IN to sync pattern of DATA0 (rx, then tx) 2 7.5 16-60 DATAx (rx) to ACK/NAK/STALL (tx) 2 7.5 16-60 */ ;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: 34 cycles -> max 25 cycles interrupt disable ;max stack usage: [ret(2), YL, SREG, YH, shift, x1, x2, x3, cnt, x4] = 11 bytes ;Numbers in brackets are maximum cycles since SOF. USB_INTR_VECTOR: ;order of registers pushed: YL, SREG [sofError], YH, shift, x1, x2, x3, cnt push YL ;2 [35] push only what is necessary to sync with edge ASAP in YL, SREG ;1 [37] push YL ;2 [39] ;---------------------------------------------------------------------------- ; 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 rjmp foundK #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 [2] lds YL, usbInputBufOffset;2 [4] clr YH ;1 [5] subi YL, lo8(-(usbRxBuf));1 [6] sbci YH, hi8(-(usbRxBuf));1 [7] sbis USBIN, USBMINUS ;1 [8] we want two bits K [sample 1 cycle too early] rjmp haveTwoBitsK ;2 [10] pop YH ;2 [11] undo the push from before rjmp waitForK ;2 [13] this was not the end of sync, retry haveTwoBitsK: ;---------------------------------------------------------------------------- ; push more registers and initialize values while we sample the first bits: ;---------------------------------------------------------------------------- push shift ;2 [16] push x1 ;2 [12] push x2 ;2 [14] in x1, USBIN ;1 [17] <-- sample bit 0 ldi shift, 0xff ;1 [18] bst x1, USBMINUS ;1 [19] bld shift, 0 ;1 [20] push x3 ;2 [22] push cnt ;2 [24] in x2, USBIN ;1 [25] <-- sample bit 1 ser x3 ;1 [26] [inserted init instruction] eor x1, x2 ;1 [27] bst x1, USBMINUS ;1 [28] bld shift, 1 ;1 [29] ldi cnt, USB_BUFSIZE;1 [30] [inserted init instruction] rjmp rxbit2 ;2 [32] ;---------------------------------------------------------------------------- ; Receiver loop (numbers in brackets are cycles within byte after instr) ;---------------------------------------------------------------------------- unstuff0: ;1 (branch taken) andi x3, ~0x01 ;1 [15] mov x1, x2 ;1 [16] x2 contains last sampled (stuffed) bit in x2, USBIN ;1 [17] <-- sample bit 1 again ori shift, 0x01 ;1 [18] rjmp didUnstuff0 ;2 [20] unstuff1: ;1 (branch taken) mov x2, x1 ;1 [21] x1 contains last sampled (stuffed) bit andi x3, ~0x02 ;1 [22] ori shift, 0x02 ;1 [23] nop ;1 [24] in x1, USBIN ;1 [25] <-- sample bit 2 again rjmp didUnstuff1 ;2 [27] unstuff2: ;1 (branch taken) andi x3, ~0x04 ;1 [29] ori shift, 0x04 ;1 [30] mov x1, x2 ;1 [31] x2 contains last sampled (stuffed) bit nop ;1 [32] in x2, USBIN ;1 [33] <-- sample bit 3 rjmp didUnstuff2 ;2 [35] unstuff3: ;1 (branch taken) in x2, USBIN ;1 [34] <-- sample stuffed bit 3 [one cycle too late] andi x3, ~0x08 ;1 [35] ori shift, 0x08 ;1 [36] rjmp didUnstuff3 ;2 [38] unstuff4: ;1 (branch taken) andi x3, ~0x10 ;1 [40] in x1, USBIN ;1 [41] <-- sample stuffed bit 4 ori shift, 0x10 ;1 [42] rjmp didUnstuff4 ;2 [44] unstuff5: ;1 (branch taken) andi x3, ~0x20 ;1 [48] in x2, USBIN ;1 [49] <-- sample stuffed bit 5 ori shift, 0x20 ;1 [50] rjmp didUnstuff5 ;2 [52] unstuff6: ;1 (branch taken) andi x3, ~0x40 ;1 [56] in x1, USBIN ;1 [57] <-- sample stuffed bit 6 ori shift, 0x40 ;1 [58] rjmp didUnstuff6 ;2 [60] ; extra jobs done during bit interval: ; bit 0: store, clear [SE0 is unreliable here due to bit dribbling in hubs] ; bit 1: se0 check ; bit 2: overflow check ; bit 3: recovery from delay [bit 0 tasks took too long] ; bit 4: none ; bit 5: none ; bit 6: none ; bit 7: jump, eor rxLoop: eor x3, shift ;1 [0] reconstruct: x3 is 0 at bit locations we changed, 1 at others in x1, USBIN ;1 [1] <-- sample bit 0 st y+, x3 ;2 [3] store data ser x3 ;1 [4] nop ;1 [5] eor x2, x1 ;1 [6] bst x2, USBMINUS;1 [7] bld shift, 0 ;1 [8] in x2, USBIN ;1 [9] <-- sample bit 1 (or possibly bit 0 stuffed) andi x2, USBMASK ;1 [10] breq se0 ;1 [11] SE0 check for bit 1 andi shift, 0xf9 ;1 [12] didUnstuff0: breq unstuff0 ;1 [13] eor x1, x2 ;1 [14] bst x1, USBMINUS;1 [15] bld shift, 1 ;1 [16] rxbit2: in x1, USBIN ;1 [17] <-- sample bit 2 (or possibly bit 1 stuffed) andi shift, 0xf3 ;1 [18] breq unstuff1 ;1 [19] do remaining work for bit 1 didUnstuff1: subi cnt, 1 ;1 [20] brcs overflow ;1 [21] loop control eor x2, x1 ;1 [22] bst x2, USBMINUS;1 [23] bld shift, 2 ;1 [24] in x2, USBIN ;1 [25] <-- sample bit 3 (or possibly bit 2 stuffed) andi shift, 0xe7 ;1 [26] breq unstuff2 ;1 [27] didUnstuff2: eor x1, x2 ;1 [28] bst x1, USBMINUS;1 [29] bld shift, 3 ;1 [30] didUnstuff3: andi shift, 0xcf ;1 [31] breq unstuff3 ;1 [32] in x1, USBIN ;1 [33] <-- sample bit 4 eor x2, x1 ;1 [34] bst x2, USBMINUS;1 [35] bld shift, 4 ;1 [36] didUnstuff4: andi shift, 0x9f ;1 [37] breq unstuff4 ;1 [38] nop2 ;2 [40] in x2, USBIN ;1 [41] <-- sample bit 5 eor x1, x2 ;1 [42] bst x1, USBMINUS;1 [43] bld shift, 5 ;1 [44] didUnstuff5: andi shift, 0x3f ;1 [45] breq unstuff5 ;1 [46] nop2 ;2 [48] in x1, USBIN ;1 [49] <-- sample bit 6 eor x2, x1 ;1 [50] bst x2, USBMINUS;1 [51] bld shift, 6 ;1 [52] didUnstuff6: cpi shift, 0x02 ;1 [53] brlo unstuff6 ;1 [54] nop2 ;2 [56] in x2, USBIN ;1 [57] <-- sample bit 7 eor x1, x2 ;1 [58] bst x1, USBMINUS;1 [59] bld shift, 7 ;1 [60] didUnstuff7: cpi shift, 0x04 ;1 [61] brsh rxLoop ;2 [63] loop control unstuff7: andi x3, ~0x80 ;1 [63] ori shift, 0x80 ;1 [64] in x2, USBIN ;1 [65] <-- sample stuffed bit 7 nop ;1 [66] rjmp didUnstuff7 ;2 [68] macro POP_STANDARD ; 12 cycles 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] [59] brcc doExorN1 ;[-4] [60] subi x4, 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: ;0 [-19] 19 cycles until SOP ldi x3, USBPID_NAK ;1 [-18] rjmp usbSendX3 ;2 [-16] sendAckAndReti: ;0 [-19] 19 cycles until SOP ldi x3, USBPID_ACK ;1 [-18] rjmp usbSendX3 ;2 [-16] sendCntAndReti: ;0 [-17] 17 cycles until SOP mov x3, cnt ;1 [-16] usbSendX3: ;0 [-16] ldi YL, 20 ;1 [-15] 'x3' is R20 ldi YH, 0 ;1 [-14] ldi cnt, 2 ;1 [-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...x2, x4, shift, cnt, Y [x1 = mirror USBOUT, x2 = USBMASK, x4 = bitstuff cnt] ;Numbers in brackets are time since first bit of sync pattern is sent (start of instruction) usbSendAndReti: in x2, USBDDR ;[-12] 12 cycles until SOP ori x2, USBMASK ;[-11] sbi USBOUT, USBMINUS ;[-10] prepare idle state; D+ and D- must have been 0 (no pullups) out USBDDR, x2 ;[-8] <--- acquire bus in x1, USBOUT ;[-7] port mirror for tx loop ldi shift, 0x40 ;[-6] sync byte is first byte sent (we enter loop after ror) ldi x2, USBMASK ;[-5] push x4 ;[-4] doExorN1: eor x1, x2 ;[-2] [06] [62] ldi x4, 6 ;[-1] [07] [63] commonN1: stuffN2Delay: out USBOUT, x1 ;[00] [08] [64] <--- set bit ror shift ;[01] brcc doExorN2 ;[02] subi x4, 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 x4, 6 ;[05] [13] commonN2: nop ;[06] [14] subi cnt, 171 ;[07] [15] trick: (3 * 171) & 0xff = 1 out USBOUT, x1 ;[08] [16] <--- set bit brcs txBitloop ;[09] [25] [41] stuff6Delay: ror shift ;[42] [50] brcc doExor6 ;[43] subi x4, 1 ;[44] brne common6 ;[45] lsl shift ;[46] compensate ror after rjmp stuffDelay nop ;[47] stuffing consists of just waiting 8 cycles rjmp stuff6Delay ;[48] after ror, C bit is reliably clear doExor6: eor x1, x2 ;[45] [53] ldi x4, 6 ;[46] common6: stuff7Delay: ror shift ;[47] [55] out USBOUT, x1 ;[48] <--- set bit brcc doExor7 ;[49] subi x4, 1 ;[50] brne common7 ;[51] lsl shift ;[52] compensate ror after rjmp stuffDelay rjmp stuff7Delay ;[53] after ror, C bit is reliably clear doExor7: eor x1, x2 ;[51] [59] ldi x4, 6 ;[52] common7: ld shift, y+ ;[53] tst cnt ;[55] out USBOUT, x1 ;[56] <--- set bit brne txByteLoop ;[57] ;make SE0: cbr x1, USBMASK ;[58] prepare SE0 [spec says EOP may be 15 to 18 cycles] lds x2, usbNewDeviceAddr;[59] lsl x2 ;[61] we compare with left shifted address subi YL, 2 + 20 ;[62] Only assign address on data packets, not ACK/NAK in x3 sbci YH, 0 ;[63] 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 pop x4 ;[10] nop2 ;[12] nop2 ;[14] 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
