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dreamcast_usb/usbdrv/usbdrvasm165.inc
Raphaël Assénat c0ea2489c0 Initial revision
2013-10-13 21:01:08 +00:00

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/* Name: usbdrvasm165.inc
* Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers
* Author: Christian Starkjohann
* Creation Date: 2007-04-22
* 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 16.5 MHz version of the USB driver. It is intended for the
ATTiny45 and similar controllers running on 16.5 MHz internal RC oscillator.
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.
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!
*/
;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: 59 cycles -> max 52 cycles interrupt disable
;max stack usage: [ret(2), r0, SREG, YL, YH, shift, x1, x2, x3, x4, cnt] = 12 bytes
;nominal frequency: 16.5 MHz -> 11 cycles per bit
; 16.3125 MHz < F_CPU < 16.6875 MHz (+/- 1.1%)
; Numbers in brackets are clocks counted from center of last sync bit
; when instruction starts
USB_INTR_VECTOR:
;order of registers pushed: YL, SREG [sofError], r0, YH, shift, x1, x2, x3, x4, cnt
push YL ;[-23] push only what is necessary to sync with edge ASAP
in YL, SREG ;[-21]
push YL ;[-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 r0 ;[-12]
; [---] ;[-11]
push YH ;[-10]
; [---] ;[-9]
lds YL, usbInputBufOffset;[-8]
; [---] ;[-7]
clr YH ;[-6]
subi YL, lo8(-(usbRxBuf));[-5] [rx loop init]
sbci YH, hi8(-(usbRxBuf));[-4] [rx loop init]
mov r0, x2 ;[-3] [rx loop init]
sbis USBIN, USBMINUS ;[-2] we want two bits K (sample 2 cycles too early)
rjmp haveTwoBitsK ;[-1]
pop YH ;[0] undo the pushes from before
pop r0 ;[2]
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 (= 22 cycles).
;----------------------------------------------------------------------------
; push more registers and initialize values while we sample the first bits:
;----------------------------------------------------------------------------
haveTwoBitsK: ;[1]
push shift ;[1]
push x1 ;[3]
push x2 ;[5]
push x3 ;[7]
ldi shift, 0xff ;[9] [rx loop init]
ori x3, 0xff ;[10] [rx loop init] == ser x3, clear zero flag
in x1, USBIN ;[11] <-- sample bit 0
bst x1, USBMINUS ;[12]
bld shift, 0 ;[13]
push x4 ;[14] == phase
; [---] ;[15]
push cnt ;[16]
; [---] ;[17]
ldi phase, 0 ;[18] [rx loop init]
ldi cnt, USB_BUFSIZE;[19] [rx loop init]
rjmp rxbit1 ;[20]
; [---] ;[21]
;----------------------------------------------------------------------------
; Receiver loop (numbers in brackets are cycles within byte after instr)
;----------------------------------------------------------------------------
/*
byte oriented operations done during loop:
bit 0: store data
bit 1: SE0 check
bit 2: overflow check
bit 3: catch up
bit 4: rjmp to achieve conditional jump range
bit 5: PLL
bit 6: catch up
bit 7: jump, fixup bitstuff
; 87 [+ 2] cycles
------------------------------------------------------------------
*/
continueWithBit5:
in x2, USBIN ;[055] <-- bit 5
eor r0, x2 ;[056]
or phase, r0 ;[057]
sbrc phase, USBMINUS ;[058]
lpm ;[059] optional nop3; modifies r0
in phase, USBIN ;[060] <-- phase
eor x1, x2 ;[061]
bst x1, USBMINUS ;[062]
bld shift, 5 ;[063]
andi shift, 0x3f ;[064]
in x1, USBIN ;[065] <-- bit 6
breq unstuff5 ;[066] *** unstuff escape
eor phase, x1 ;[067]
eor x2, x1 ;[068]
bst x2, USBMINUS ;[069]
bld shift, 6 ;[070]
didUnstuff6: ;[ ]
in r0, USBIN ;[071] <-- phase
cpi shift, 0x02 ;[072]
brlo unstuff6 ;[073] *** unstuff escape
didUnstuff5: ;[ ]
nop2 ;[074]
; [---] ;[075]
in x2, USBIN ;[076] <-- bit 7
eor x1, x2 ;[077]
bst x1, USBMINUS ;[078]
bld shift, 7 ;[079]
didUnstuff7: ;[ ]
eor r0, x2 ;[080]
or phase, r0 ;[081]
in r0, USBIN ;[082] <-- phase
cpi shift, 0x04 ;[083]
brsh rxLoop ;[084]
; [---] ;[085]
unstuff7: ;[ ]
andi x3, ~0x80 ;[085]
ori shift, 0x80 ;[086]
in x2, USBIN ;[087] <-- sample stuffed bit 7
nop ;[088]
rjmp didUnstuff7 ;[089]
; [---] ;[090]
;[080]
unstuff5: ;[067]
eor phase, x1 ;[068]
andi x3, ~0x20 ;[069]
ori shift, 0x20 ;[070]
in r0, USBIN ;[071] <-- phase
mov x2, x1 ;[072]
nop ;[073]
nop2 ;[074]
; [---] ;[075]
in x1, USBIN ;[076] <-- bit 6
eor r0, x1 ;[077]
or phase, r0 ;[078]
eor x2, x1 ;[079]
bst x2, USBMINUS ;[080]
bld shift, 6 ;[081] no need to check bitstuffing, we just had one
in r0, USBIN ;[082] <-- phase
rjmp didUnstuff5 ;[083]
; [---] ;[084]
;[074]
unstuff6: ;[074]
andi x3, ~0x40 ;[075]
in x1, USBIN ;[076] <-- bit 6 again
ori shift, 0x40 ;[077]
nop2 ;[078]
; [---] ;[079]
rjmp didUnstuff6 ;[080]
; [---] ;[081]
;[071]
unstuff0: ;[013]
eor r0, x2 ;[014]
or phase, r0 ;[015]
andi x2, USBMASK ;[016] check for SE0
in r0, USBIN ;[017] <-- phase
breq didUnstuff0 ;[018] direct jump to se0 would be too long
andi x3, ~0x01 ;[019]
ori shift, 0x01 ;[020]
mov x1, x2 ;[021] mov existing sample
in x2, USBIN ;[022] <-- bit 1 again
rjmp didUnstuff0 ;[023]
; [---] ;[024]
;[014]
unstuff1: ;[024]
eor r0, x1 ;[025]
or phase, r0 ;[026]
andi x3, ~0x02 ;[027]
in r0, USBIN ;[028] <-- phase
ori shift, 0x02 ;[029]
mov x2, x1 ;[030]
rjmp didUnstuff1 ;[031]
; [---] ;[032]
;[022]
unstuff2: ;[035]
eor r0, x2 ;[036]
or phase, r0 ;[037]
andi x3, ~0x04 ;[038]
in r0, USBIN ;[039] <-- phase
ori shift, 0x04 ;[040]
mov x1, x2 ;[041]
rjmp didUnstuff2 ;[042]
; [---] ;[043]
;[033]
unstuff3: ;[043]
in x2, USBIN ;[044] <-- bit 3 again
eor r0, x2 ;[045]
or phase, r0 ;[046]
andi x3, ~0x08 ;[047]
ori shift, 0x08 ;[048]
nop ;[049]
in r0, USBIN ;[050] <-- phase
rjmp didUnstuff3 ;[051]
; [---] ;[052]
;[042]
unstuff4: ;[053]
andi x3, ~0x10 ;[054]
in x1, USBIN ;[055] <-- bit 4 again
ori shift, 0x10 ;[056]
rjmp didUnstuff4 ;[057]
; [---] ;[058]
;[048]
rxLoop: ;[085]
eor x3, shift ;[086] reconstruct: x3 is 0 at bit locations we changed, 1 at others
in x1, USBIN ;[000] <-- bit 0
st y+, x3 ;[001]
; [---] ;[002]
eor r0, x1 ;[003]
or phase, r0 ;[004]
eor x2, x1 ;[005]
in r0, USBIN ;[006] <-- phase
ser x3 ;[007]
bst x2, USBMINUS ;[008]
bld shift, 0 ;[009]
andi shift, 0xf9 ;[010]
rxbit1: ;[ ]
in x2, USBIN ;[011] <-- bit 1
breq unstuff0 ;[012] *** unstuff escape
andi x2, USBMASK ;[013] SE0 check for bit 1
didUnstuff0: ;[ ] Z only set if we detected SE0 in bitstuff
breq se0 ;[014]
eor r0, x2 ;[015]
or phase, r0 ;[016]
in r0, USBIN ;[017] <-- phase
eor x1, x2 ;[018]
bst x1, USBMINUS ;[019]
bld shift, 1 ;[020]
andi shift, 0xf3 ;[021]
didUnstuff1: ;[ ]
in x1, USBIN ;[022] <-- bit 2
breq unstuff1 ;[023] *** unstuff escape
eor r0, x1 ;[024]
or phase, r0 ;[025]
subi cnt, 1 ;[026] overflow check
brcs overflow ;[027]
in r0, USBIN ;[028] <-- phase
eor x2, x1 ;[029]
bst x2, USBMINUS ;[030]
bld shift, 2 ;[031]
andi shift, 0xe7 ;[032]
didUnstuff2: ;[ ]
in x2, USBIN ;[033] <-- bit 3
breq unstuff2 ;[034] *** unstuff escape
eor r0, x2 ;[035]
or phase, r0 ;[036]
eor x1, x2 ;[037]
bst x1, USBMINUS ;[038]
in r0, USBIN ;[039] <-- phase
bld shift, 3 ;[040]
andi shift, 0xcf ;[041]
didUnstuff3: ;[ ]
breq unstuff3 ;[042] *** unstuff escape
nop ;[043]
in x1, USBIN ;[044] <-- bit 4
eor x2, x1 ;[045]
bst x2, USBMINUS ;[046]
bld shift, 4 ;[047]
didUnstuff4: ;[ ]
eor r0, x1 ;[048]
or phase, r0 ;[049]
in r0, USBIN ;[050] <-- phase
andi shift, 0x9f ;[051]
breq unstuff4 ;[052] *** unstuff escape
rjmp continueWithBit5;[053]
; [---] ;[054]
macro POP_STANDARD ; 16 cycles
pop cnt
pop x4
pop x3
pop x2
pop x1
pop shift
pop YH
pop r0
endm
macro POP_RETI ; 5 cycles
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
bitstuff7:
eor x1, x4 ;[4]
ldi x2, 0 ;[5]
nop2 ;[6] C is zero (brcc)
rjmp didStuff7 ;[8]
bitstuffN:
eor x1, x4 ;[5]
ldi x2, 0 ;[6]
lpm ;[7] 3 cycle NOP, modifies r0
out USBOUT, x1 ;[10] <-- out
rjmp didStuffN ;[0]
#define bitStatus x3
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
;usbSend:
;pointer to data in 'Y'
;number of bytes in 'cnt' -- including sync byte [range 2 ... 12]
;uses: x1...x4, shift, cnt, Y
;Numbers in brackets are time since first bit of sync pattern is sent
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
ldi bitStatus, 0xff ;[-4] init bit loop counter, works for up to 12 bytes
byteloop:
bitloop:
sbrs shift, 0 ;[8] [-3]
eor x1, x4 ;[9] [-2]
out USBOUT, x1 ;[10] [-1] <-- out
ror shift ;[0]
ror x2 ;[1]
didStuffN:
cpi x2, 0xfc ;[2]
brcc bitstuffN ;[3]
nop ;[4]
subi bitStatus, 37 ;[5] 256 / 7 ~=~ 37
brcc bitloop ;[6] when we leave the loop, bitStatus has almost the initial value
sbrs shift, 0 ;[7]
eor x1, x4 ;[8]
ror shift ;[9]
didStuff7:
out USBOUT, x1 ;[10] <-- out
ror x2 ;[0]
cpi x2, 0xfc ;[1]
brcc bitstuff7 ;[2]
ld shift, y+ ;[3]
dec cnt ;[5]
brne byteloop ;[6]
;make SE0:
cbr x1, USBMASK ;[7] prepare SE0 [spec says EOP may be 21 to 25 cycles]
lds x2, usbNewDeviceAddr;[8]
lsl x2 ;[10] we compare with left shifted address
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
subi YL, 2 ;[0] Only assign address on data packets, not ACK/NAK in r0
sbci YH, 0 ;[1]
breq skipAddrAssign ;[2]
sts usbDeviceAddr, x2; if not skipped: SE0 is one cycle longer
skipAddrAssign:
;end of usbDeviceAddress transfer
ldi x2, 1<<USB_INTR_PENDING_BIT;[4] int0 occurred during TX -- clear pending flag
USB_STORE_PENDING(x2) ;[5]
ori x1, USBIDLE ;[6]
in x2, USBDDR ;[7]
cbr x2, USBMASK ;[8] set both pins to input
mov x3, x1 ;[9]
cbr x3, USBMASK ;[10] configure no pullup on both pins
ldi x4, 4 ;[11]
se0Delay:
dec x4 ;[12] [15] [18] [21]
brne se0Delay ;[13] [16] [19] [22]
out USBOUT, x1 ;[23] <-- out J (idle) -- end of SE0 (EOP signal)
out USBDDR, x2 ;[24] <-- release bus now
out USBOUT, x3 ;[25] <-- ensure no pull-up resistors are active
rjmp doReturn
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