diff options
Diffstat (limited to 'vusb/usbdrv/usbdrvasm16.inc')
| -rw-r--r-- | vusb/usbdrv/usbdrvasm16.inc | 346 |
1 files changed, 346 insertions, 0 deletions
diff --git a/vusb/usbdrv/usbdrvasm16.inc b/vusb/usbdrv/usbdrvasm16.inc new file mode 100644 index 0000000000..207b6e48a1 --- /dev/null +++ b/vusb/usbdrv/usbdrvasm16.inc @@ -0,0 +1,346 @@ +/* Name: usbdrvasm16.inc + * Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers + * Author: Christian Starkjohann + * Creation Date: 2007-06-15 + * Tabsize: 4 + * Copyright: (c) 2007 by OBJECTIVE DEVELOPMENT Software GmbH + * License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt) + * Revision: $Id: usbdrvasm16.inc 760 2009-08-09 18:59:43Z cs $ + */ + +/* Do not link this file! Link usbdrvasm.S instead, which includes the + * appropriate implementation! + */ + +/* +General Description: +This file is the 16 MHz version of the asssembler part of the USB driver. It +requires a 16 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! +*/ + +;max stack usage: [ret(2), YL, SREG, YH, bitcnt, shift, x1, x2, x3, x4, cnt] = 12 bytes +;nominal frequency: 16 MHz -> 10.6666666 cycles per bit, 85.333333333 cycles per byte +; Numbers in brackets are clocks counted from center of last sync bit +; when instruction starts + +USB_INTR_VECTOR: +;order of registers pushed: YL, SREG YH, [sofError], bitcnt, shift, x1, x2, x3, x4, cnt + push YL ;[-25] push only what is necessary to sync with edge ASAP + in YL, SREG ;[-23] + push YL ;[-22] + push YH ;[-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 +;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 ;[-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 +#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: ;[-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 bitcnt ;[-12] +; [---] ;[-11] + lds YL, usbInputBufOffset;[-10] +; [---] ;[-9] + clr YH ;[-8] + subi YL, lo8(-(usbRxBuf));[-7] [rx loop init] + sbci YH, hi8(-(usbRxBuf));[-6] [rx loop init] + push shift ;[-5] +; [---] ;[-4] + ldi bitcnt, 0x55 ;[-3] [rx loop init] + sbis USBIN, USBMINUS ;[-2] we want two bits K (sample 2 cycles too early) + rjmp haveTwoBitsK ;[-1] + pop shift ;[0] undo the push from before + pop bitcnt ;[2] undo the push from before + 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 (= 21 cycles). + +;---------------------------------------------------------------------------- +; push more registers and initialize values while we sample the first bits: +;---------------------------------------------------------------------------- +haveTwoBitsK: + push x1 ;[1] + push x2 ;[3] + push x3 ;[5] + ldi shift, 0 ;[7] + ldi x3, 1<<4 ;[8] [rx loop init] first sample is inverse bit, compensate that + push x4 ;[9] == leap + + in x1, USBIN ;[11] <-- sample bit 0 + andi x1, USBMASK ;[12] + bst x1, USBMINUS ;[13] + bld shift, 7 ;[14] + push cnt ;[15] + ldi leap, 0 ;[17] [rx loop init] + ldi cnt, USB_BUFSIZE;[18] [rx loop init] + rjmp rxbit1 ;[19] arrives at [21] + +;---------------------------------------------------------------------------- +; Receiver loop (numbers in brackets are cycles within byte after instr) +;---------------------------------------------------------------------------- + +; duration of unstuffing code should be 10.66666667 cycles. We adjust "leap" +; accordingly to approximate this value in the long run. + +unstuff6: + andi x2, USBMASK ;[03] + ori x3, 1<<6 ;[04] will not be shifted any more + andi shift, ~0x80;[05] + mov x1, x2 ;[06] sampled bit 7 is actually re-sampled bit 6 + subi leap, -1 ;[07] total duration = 11 bits -> subtract 1/3 + rjmp didUnstuff6 ;[08] + +unstuff7: + ori x3, 1<<7 ;[09] will not be shifted any more + in x2, USBIN ;[00] [10] re-sample bit 7 + andi x2, USBMASK ;[01] + andi shift, ~0x80;[02] + subi leap, 2 ;[03] total duration = 10 bits -> add 1/3 + rjmp didUnstuff7 ;[04] + +unstuffEven: + ori x3, 1<<6 ;[09] will be shifted right 6 times for bit 0 + in x1, USBIN ;[00] [10] + andi shift, ~0x80;[01] + andi x1, USBMASK ;[02] + breq se0 ;[03] + subi leap, -1 ;[04] total duration = 11 bits -> subtract 1/3 + nop2 ;[05] + rjmp didUnstuffE ;[06] + +unstuffOdd: + ori x3, 1<<5 ;[09] will be shifted right 4 times for bit 1 + in x2, USBIN ;[00] [10] + andi shift, ~0x80;[01] + andi x2, USBMASK ;[02] + breq se0 ;[03] + subi leap, -1 ;[04] total duration = 11 bits -> subtract 1/3 + nop2 ;[05] + rjmp didUnstuffO ;[06] + +rxByteLoop: + andi x1, USBMASK ;[03] + eor x2, x1 ;[04] + subi leap, 1 ;[05] + brpl skipLeap ;[06] + subi leap, -3 ;1 one leap cycle every 3rd byte -> 85 + 1/3 cycles per byte + nop ;1 +skipLeap: + subi x2, 1 ;[08] + ror shift ;[09] +didUnstuff6: + cpi shift, 0xfc ;[10] + in x2, USBIN ;[00] [11] <-- sample bit 7 + brcc unstuff6 ;[01] + andi x2, USBMASK ;[02] + eor x1, x2 ;[03] + subi x1, 1 ;[04] + ror shift ;[05] +didUnstuff7: + cpi shift, 0xfc ;[06] + brcc unstuff7 ;[07] + eor x3, shift ;[08] reconstruct: x3 is 1 at bit locations we changed, 0 at others + st y+, x3 ;[09] store data +rxBitLoop: + in x1, USBIN ;[00] [11] <-- sample bit 0/2/4 + andi x1, USBMASK ;[01] + eor x2, x1 ;[02] + andi x3, 0x3f ;[03] topmost two bits reserved for 6 and 7 + subi x2, 1 ;[04] + ror shift ;[05] + cpi shift, 0xfc ;[06] + brcc unstuffEven ;[07] +didUnstuffE: + lsr x3 ;[08] + lsr x3 ;[09] +rxbit1: + in x2, USBIN ;[00] [10] <-- sample bit 1/3/5 + andi x2, USBMASK ;[01] + breq se0 ;[02] + eor x1, x2 ;[03] + subi x1, 1 ;[04] + ror shift ;[05] + cpi shift, 0xfc ;[06] + brcc unstuffOdd ;[07] +didUnstuffO: + subi bitcnt, 0xab;[08] == addi 0x55, 0x55 = 0x100/3 + brcs rxBitLoop ;[09] + + subi cnt, 1 ;[10] + in x1, USBIN ;[00] [11] <-- sample bit 6 + brcc rxByteLoop ;[01] + rjmp overflow + +macro POP_STANDARD ; 14 cycles + pop cnt + pop x4 + pop x3 + pop x2 + pop x1 + pop shift + pop bitcnt + endm +macro POP_RETI ; 7 cycles + pop YH + pop YL + out SREG, YL + pop YL + endm + +#include "asmcommon.inc" + +; 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 + +bitstuffN: + eor x1, x4 ;[5] + ldi x2, 0 ;[6] + nop2 ;[7] + nop ;[9] + out USBOUT, x1 ;[10] <-- out + rjmp didStuffN ;[0] + +bitstuff6: + eor x1, x4 ;[5] + ldi x2, 0 ;[6] Carry is zero due to brcc + rol shift ;[7] compensate for ror shift at branch destination + rjmp didStuff6 ;[8] + +bitstuff7: + ldi x2, 0 ;[2] Carry is zero due to brcc + rjmp didStuff7 ;[3] + + +sendNakAndReti: + ldi x3, USBPID_NAK ;[-18] + rjmp sendX3AndReti ;[-17] +sendAckAndReti: + ldi cnt, USBPID_ACK ;[-17] +sendCntAndReti: + mov x3, cnt ;[-16] +sendX3AndReti: + ldi YL, 20 ;[-15] x3==r20 address is 20 + 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, btcnt, shift, cnt, Y +;Numbers in brackets are time since first bit of sync pattern is sent +;We don't match the transfer rate exactly (don't insert leap cycles every third +;byte) because the spec demands only 1.5% precision anyway. +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 +txByteLoop: + ldi bitcnt, 0x35 ;[-4] [6] binary 0011 0101 +txBitLoop: + sbrs shift, 0 ;[-3] [7] + eor x1, x4 ;[-2] [8] + out USBOUT, x1 ;[-1] [9] <-- out N + ror shift ;[0] [10] + ror x2 ;[1] +didStuffN: + cpi x2, 0xfc ;[2] + brcc bitstuffN ;[3] + lsr bitcnt ;[4] + brcc txBitLoop ;[5] + brne txBitLoop ;[6] + + sbrs shift, 0 ;[7] + eor x1, x4 ;[8] +didStuff6: + out USBOUT, x1 ;[-1] [9] <-- out 6 + ror shift ;[0] [10] + ror x2 ;[1] + cpi x2, 0xfc ;[2] + brcc bitstuff6 ;[3] + ror shift ;[4] +didStuff7: + ror x2 ;[5] + sbrs x2, 7 ;[6] + eor x1, x4 ;[7] + nop ;[8] + cpi x2, 0xfc ;[9] + out USBOUT, x1 ;[-1][10] <-- out 7 + brcc bitstuff7 ;[0] [11] + ld shift, y+ ;[1] + dec cnt ;[3] + brne txByteLoop ;[4] +;make SE0: + cbr x1, USBMASK ;[5] prepare SE0 [spec says EOP may be 21 to 25 cycles] + lds x2, usbNewDeviceAddr;[6] + lsl x2 ;[8] we compare with left shifted address + subi YL, 20 + 2 ;[9] Only assign address on data packets, not ACK/NAK in x3 + sbci YH, 0 ;[10] + out USBOUT, x1 ;[11] <-- 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 + breq skipAddrAssign ;[0] + sts usbDeviceAddr, x2; if not skipped: SE0 is one cycle longer +skipAddrAssign: +;end of usbDeviceAddress transfer + ldi x2, 1<<USB_INTR_PENDING_BIT;[2] int0 occurred during TX -- clear pending flag + USB_STORE_PENDING(x2) ;[3] + ori x1, USBIDLE ;[4] + in x2, USBDDR ;[5] + cbr x2, USBMASK ;[6] set both pins to input + mov x3, x1 ;[7] + cbr x3, USBMASK ;[8] configure no pullup on both pins + ldi x4, 4 ;[9] +se0Delay: + dec x4 ;[10] [13] [16] [19] + brne se0Delay ;[11] [14] [17] [20] + out USBOUT, x1 ;[21] <-- out J (idle) -- end of SE0 (EOP signal) + out USBDDR, x2 ;[22] <-- release bus now + out USBOUT, x3 ;[23] <-- ensure no pull-up resistors are active + rjmp doReturn |