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dreamcast_usb/usbdrv/usbdrvasm15.inc

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/* Name: usbdrvasm15.inc
* Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers
* Author: contributed by V. Bosch
* Creation Date: 2007-08-06
* 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 15 MHz version of the asssembler part of the USB driver. It
requires a 15 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: 15 MHz -> 10.0 cycles per bit, 80.0 cycles per byte
; Numbers in brackets are clocks counted from center of last sync bit
; when instruction starts
;----------------------------------------------------------------------------
; order of registers pushed:
; YL, SREG [sofError] YH, shift, x1, x2, x3, bitcnt, cnt, x4
;----------------------------------------------------------------------------
USB_INTR_VECTOR:
push YL ;2 push only what is necessary to sync with edge ASAP
in YL, SREG ;1
push YL ;2
;----------------------------------------------------------------------------
; 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
;-------------------------------------------------------------------------------
; The following code results in a sampling window of < 1/4 bit
; which meets the spec.
;-------------------------------------------------------------------------------
waitForK: ;-
sbis USBIN, USBMINUS ;1 [00] <-- sample
rjmp foundK ;2 [01]
sbis USBIN, USBMINUS ; <-- sample
rjmp foundK
sbis USBIN, USBMINUS ; <-- sample
rjmp foundK
sbis USBIN, USBMINUS ; <-- sample
rjmp foundK
sbis USBIN, USBMINUS ; <-- sample
rjmp foundK
sbis USBIN, USBMINUS ; <-- sample
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
;------------------------------------------------------------------------------
; {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
;------------------------------------------------------------------------------
foundK: ;- [02]
lds YL, usbInputBufOffset;2 [03+04] tx loop
push YH ;2 [05+06]
clr YH ;1 [07]
subi YL, lo8(-(usbRxBuf)) ;1 [08] [rx loop init]
sbci YH, hi8(-(usbRxBuf)) ;1 [09] [rx loop init]
push shift ;2 [10+11]
ser shift ;1 [12]
sbis USBIN, USBMINUS ;1 [-1] [13] <--sample:we want two bits K (sample 1 cycle too early)
rjmp haveTwoBitsK ;2 [00] [14]
pop shift ;2 [15+16] undo the push from before
pop YH ;2 [17+18] undo the push from before
rjmp waitForK ;2 [19+20] this was not the end of sync, retry
; The entire loop from waitForK until rjmp waitForK above must not exceed two
; bit times (= 20 cycles).
;----------------------------------------------------------------------------
; push more registers and initialize values while we sample the first bits:
;----------------------------------------------------------------------------
haveTwoBitsK: ;- [01]
push x1 ;2 [02+03]
push x2 ;2 [04+05]
push x3 ;2 [06+07]
push bitcnt ;2 [08+09]
in x1, USBIN ;1 [00] [10] <-- sample bit 0
bst x1, USBMINUS ;1 [01]
bld shift, 0 ;1 [02]
push cnt ;2 [03+04]
ldi cnt, USB_BUFSIZE ;1 [05]
push x4 ;2 [06+07] tx loop
rjmp rxLoop ;2 [08]
;----------------------------------------------------------------------------
; Receiver loop (numbers in brackets are cycles within byte after instr)
;----------------------------------------------------------------------------
unstuff0: ;- [07] (branch taken)
andi x3, ~0x01 ;1 [08]
mov x1, x2 ;1 [09] x2 contains last sampled (stuffed) bit
in x2, USBIN ;1 [00] [10] <-- sample bit 1 again
andi x2, USBMASK ;1 [01]
breq se0Hop ;1 [02] SE0 check for bit 1
ori shift, 0x01 ;1 [03] 0b00000001
nop ;1 [04]
rjmp didUnstuff0 ;2 [05]
;-----------------------------------------------------
unstuff1: ;- [05] (branch taken)
mov x2, x1 ;1 [06] x1 contains last sampled (stuffed) bit
andi x3, ~0x02 ;1 [07]
ori shift, 0x02 ;1 [08] 0b00000010
nop ;1 [09]
in x1, USBIN ;1 [00] [10] <-- sample bit 2 again
andi x1, USBMASK ;1 [01]
breq se0Hop ;1 [02] SE0 check for bit 2
rjmp didUnstuff1 ;2 [03]
;-----------------------------------------------------
unstuff2: ;- [05] (branch taken)
andi x3, ~0x04 ;1 [06]
ori shift, 0x04 ;1 [07] 0b00000100
mov x1, x2 ;1 [08] x2 contains last sampled (stuffed) bit
nop ;1 [09]
in x2, USBIN ;1 [00] [10] <-- sample bit 3
andi x2, USBMASK ;1 [01]
breq se0Hop ;1 [02] SE0 check for bit 3
rjmp didUnstuff2 ;2 [03]
;-----------------------------------------------------
unstuff3: ;- [00] [10] (branch taken)
in x2, USBIN ;1 [01] [11] <-- sample stuffed bit 3 one cycle too late
andi x2, USBMASK ;1 [02]
breq se0Hop ;1 [03] SE0 check for stuffed bit 3
andi x3, ~0x08 ;1 [04]
ori shift, 0x08 ;1 [05] 0b00001000
rjmp didUnstuff3 ;2 [06]
;----------------------------------------------------------------------------
; extra jobs done during bit interval:
;
; bit 0: store, clear [SE0 is unreliable here due to bit dribbling in hubs],
; overflow check, jump to the head of rxLoop
; bit 1: SE0 check
; bit 2: SE0 check, recovery from delay [bit 0 tasks took too long]
; bit 3: SE0 check, recovery from delay [bit 0 tasks took too long]
; bit 4: SE0 check, none
; bit 5: SE0 check, none
; bit 6: SE0 check, none
; bit 7: SE0 check, reconstruct: x3 is 0 at bit locations we changed, 1 at others
;----------------------------------------------------------------------------
rxLoop: ;- [09]
in x2, USBIN ;1 [00] [10] <-- sample bit 1 (or possibly bit 0 stuffed)
andi x2, USBMASK ;1 [01]
brne SkipSe0Hop ;1 [02]
se0Hop: ;- [02]
rjmp se0 ;2 [03] SE0 check for bit 1
SkipSe0Hop: ;- [03]
ser x3 ;1 [04]
andi shift, 0xf9 ;1 [05] 0b11111001
breq unstuff0 ;1 [06]
didUnstuff0: ;- [06]
eor x1, x2 ;1 [07]
bst x1, USBMINUS ;1 [08]
bld shift, 1 ;1 [09]
in x1, USBIN ;1 [00] [10] <-- sample bit 2 (or possibly bit 1 stuffed)
andi x1, USBMASK ;1 [01]
breq se0Hop ;1 [02] SE0 check for bit 2
andi shift, 0xf3 ;1 [03] 0b11110011
breq unstuff1 ;1 [04] do remaining work for bit 1
didUnstuff1: ;- [04]
eor x2, x1 ;1 [05]
bst x2, USBMINUS ;1 [06]
bld shift, 2 ;1 [07]
nop2 ;2 [08+09]
in x2, USBIN ;1 [00] [10] <-- sample bit 3 (or possibly bit 2 stuffed)
andi x2, USBMASK ;1 [01]
breq se0Hop ;1 [02] SE0 check for bit 3
andi shift, 0xe7 ;1 [03] 0b11100111
breq unstuff2 ;1 [04]
didUnstuff2: ;- [04]
eor x1, x2 ;1 [05]
bst x1, USBMINUS ;1 [06]
bld shift, 3 ;1 [07]
didUnstuff3: ;- [07]
andi shift, 0xcf ;1 [08] 0b11001111
breq unstuff3 ;1 [09]
in x1, USBIN ;1 [00] [10] <-- sample bit 4
andi x1, USBMASK ;1 [01]
breq se0Hop ;1 [02] SE0 check for bit 4
eor x2, x1 ;1 [03]
bst x2, USBMINUS ;1 [04]
bld shift, 4 ;1 [05]
didUnstuff4: ;- [05]
andi shift, 0x9f ;1 [06] 0b10011111
breq unstuff4 ;1 [07]
nop2 ;2 [08+09]
in x2, USBIN ;1 [00] [10] <-- sample bit 5
andi x2, USBMASK ;1 [01]
breq se0 ;1 [02] SE0 check for bit 5
eor x1, x2 ;1 [03]
bst x1, USBMINUS ;1 [04]
bld shift, 5 ;1 [05]
didUnstuff5: ;- [05]
andi shift, 0x3f ;1 [06] 0b00111111
breq unstuff5 ;1 [07]
nop2 ;2 [08+09]
in x1, USBIN ;1 [00] [10] <-- sample bit 6
andi x1, USBMASK ;1 [01]
breq se0 ;1 [02] SE0 check for bit 6
eor x2, x1 ;1 [03]
bst x2, USBMINUS ;1 [04]
bld shift, 6 ;1 [05]
didUnstuff6: ;- [05]
cpi shift, 0x02 ;1 [06] 0b00000010
brlo unstuff6 ;1 [07]
nop2 ;2 [08+09]
in x2, USBIN ;1 [00] [10] <-- sample bit 7
andi x2, USBMASK ;1 [01]
breq se0 ;1 [02] SE0 check for bit 7
eor x1, x2 ;1 [03]
bst x1, USBMINUS ;1 [04]
bld shift, 7 ;1 [05]
didUnstuff7: ;- [05]
cpi shift, 0x04 ;1 [06] 0b00000100
brlo unstuff7 ;1 [07]
eor x3, shift ;1 [08] reconstruct: x3 is 0 at bit locations we changed, 1 at others
nop ;1 [09]
in x1, USBIN ;1 [00] [10] <-- sample bit 0
st y+, x3 ;2 [01+02] store data
eor x2, x1 ;1 [03]
bst x2, USBMINUS ;1 [04]
bld shift, 0 ;1 [05]
subi cnt, 1 ;1 [06]
brcs overflow ;1 [07]
rjmp rxLoop ;2 [08]
;-----------------------------------------------------
unstuff4: ;- [08]
andi x3, ~0x10 ;1 [09]
in x1, USBIN ;1 [00] [10] <-- sample stuffed bit 4
andi x1, USBMASK ;1 [01]
breq se0 ;1 [02] SE0 check for stuffed bit 4
ori shift, 0x10 ;1 [03]
rjmp didUnstuff4 ;2 [04]
;-----------------------------------------------------
unstuff5: ;- [08]
ori shift, 0x20 ;1 [09]
in x2, USBIN ;1 [00] [10] <-- sample stuffed bit 5
andi x2, USBMASK ;1 [01]
breq se0 ;1 [02] SE0 check for stuffed bit 5
andi x3, ~0x20 ;1 [03]
rjmp didUnstuff5 ;2 [04]
;-----------------------------------------------------
unstuff6: ;- [08]
andi x3, ~0x40 ;1 [09]
in x1, USBIN ;1 [00] [10] <-- sample stuffed bit 6
andi x1, USBMASK ;1 [01]
breq se0 ;1 [02] SE0 check for stuffed bit 6
ori shift, 0x40 ;1 [03]
rjmp didUnstuff6 ;2 [04]
;-----------------------------------------------------
unstuff7: ;- [08]
andi x3, ~0x80 ;1 [09]
in x2, USBIN ;1 [00] [10] <-- sample stuffed bit 7
andi x2, USBMASK ;1 [01]
breq se0 ;1 [02] SE0 check for stuffed bit 7
ori shift, 0x80 ;1 [03]
rjmp didUnstuff7 ;2 [04]
macro POP_STANDARD ; 16 cycles
pop x4
pop cnt
pop bitcnt
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"
;---------------------------------------------------------------------------
; 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: ;- [04]
eor x1, x4 ;1 [05]
clr x2 ;1 [06]
nop ;1 [07]
rjmp didStuffN ;1 [08]
;---------------------------------------------------------------------------
bitstuff6: ;- [04]
eor x1, x4 ;1 [05]
clr x2 ;1 [06]
rjmp didStuff6 ;1 [07]
;---------------------------------------------------------------------------
bitstuff7: ;- [02]
eor x1, x4 ;1 [03]
clr x2 ;1 [06]
nop ;1 [05]
rjmp didStuff7 ;1 [06]
;---------------------------------------------------------------------------
sendNakAndReti: ;- [-19]
ldi x3, USBPID_NAK ;1 [-18]
rjmp sendX3AndReti ;1 [-17]
;---------------------------------------------------------------------------
sendAckAndReti: ;- [-17]
ldi cnt, USBPID_ACK ;1 [-16]
sendCntAndReti: ;- [-16]
mov x3, cnt ;1 [-15]
sendX3AndReti: ;- [-15]
ldi YL, 20 ;1 [-14] x3==r20 address is 20
ldi YH, 0 ;1 [-13]
ldi cnt, 2 ;1 [-12]
; 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 need not to match the transfer rate exactly because the spec demands
;only 1.5% precision anyway.
usbSendAndReti: ;- [-13] 13 cycles until SOP
in x2, USBDDR ;1 [-12]
ori x2, USBMASK ;1 [-11]
sbi USBOUT, USBMINUS ;2 [-09-10] prepare idle state; D+ and D- must have been 0 (no pullups)
in x1, USBOUT ;1 [-08] port mirror for tx loop
out USBDDR, x2 ;1 [-07] <- acquire bus
; need not init x2 (bitstuff history) because sync starts with 0
ldi x4, USBMASK ;1 [-06] exor mask
ldi shift, 0x80 ;1 [-05] sync byte is first byte sent
ldi bitcnt, 6 ;1 [-04]
txBitLoop: ;- [-04] [06]
sbrs shift, 0 ;1 [-03] [07]
eor x1, x4 ;1 [-02] [08]
ror shift ;1 [-01] [09]
didStuffN: ;- [09]
out USBOUT, x1 ;1 [00] [10] <-- out N
ror x2 ;1 [01]
cpi x2, 0xfc ;1 [02]
brcc bitstuffN ;1 [03]
dec bitcnt ;1 [04]
brne txBitLoop ;1 [05]
sbrs shift, 0 ;1 [06]
eor x1, x4 ;1 [07]
ror shift ;1 [08]
didStuff6: ;- [08]
nop ;1 [09]
out USBOUT, x1 ;1 [00] [10] <-- out 6
ror x2 ;1 [01]
cpi x2, 0xfc ;1 [02]
brcc bitstuff6 ;1 [03]
sbrs shift, 0 ;1 [04]
eor x1, x4 ;1 [05]
ror shift ;1 [06]
ror x2 ;1 [07]
didStuff7: ;- [07]
ldi bitcnt, 6 ;1 [08]
cpi x2, 0xfc ;1 [09]
out USBOUT, x1 ;1 [00] [10] <-- out 7
brcc bitstuff7 ;1 [01]
ld shift, y+ ;2 [02+03]
dec cnt ;1 [04]
brne txBitLoop ;1 [05]
makeSE0:
cbr x1, USBMASK ;1 [06] prepare SE0 [spec says EOP may be 19 to 23 cycles]
lds x2, usbNewDeviceAddr;2 [07+08]
lsl x2 ;1 [09] we compare with left shifted address
;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
out USBOUT, x1 ;1 [00] [10] <-- out SE0-- from now 2 bits==20 cycl. until bus idle
subi YL, 20 + 2 ;1 [01] Only assign address on data packets, not ACK/NAK in x3
sbci YH, 0 ;1 [02]
breq skipAddrAssign ;1 [03]
sts usbDeviceAddr, x2 ;2 [04+05] if not skipped: SE0 is one cycle longer
;----------------------------------------------------------------------------
;end of usbDeviceAddress transfer
skipAddrAssign: ;- [03/04]
ldi x2, 1<<USB_INTR_PENDING_BIT ;1 [05] int0 occurred during TX -- clear pending flag
USB_STORE_PENDING(x2) ;1 [06]
ori x1, USBIDLE ;1 [07]
in x2, USBDDR ;1 [08]
cbr x2, USBMASK ;1 [09] set both pins to input
mov x3, x1 ;1 [10]
cbr x3, USBMASK ;1 [11] configure no pullup on both pins
ldi x4, 3 ;1 [12]
se0Delay: ;- [12] [15]
dec x4 ;1 [13] [16]
brne se0Delay ;1 [14] [17]
nop2 ;2 [18+19]
out USBOUT, x1 ;1 [20] <--out J (idle) -- end of SE0 (EOP sig.)
out USBDDR, x2 ;1 [21] <--release bus now
out USBOUT, x3 ;1 [22] <--ensure no pull-up resistors are active
rjmp doReturn ;1 [23]
;---------------------------------------------------------------------------
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