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/* Name:
* Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers
* Author: Christian Starkjohann
* Creation Date: 2007-11-05
* 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 contains assembler code which is shared among the USB driver
implementations for different CPU cocks. Since the code must be inserted
in the middle of the module, it's split out into this file and #included.
Jump destinations called from outside:
sofError: Called when no start sequence was found.
se0: Called when a package has been successfully received.
overflow: Called when receive buffer overflows.
doReturn: Called after sending data.
Outside jump destinations used by this module:
waitForJ: Called to receive an already arriving packet.
The following macros must be defined before this file is included:
.macro POP_RETI
#define token x1
USB_STORE_PENDING(x2) ; clear any pending interrupts
clr token
rjmp storeTokenAndReturn
; Processing of received packet (numbers in brackets are cycles after center of SE0)
;This is the only non-error exit point for the software receiver loop
;we don't check any CRCs here because there is no time left.
subi cnt, USB_BUFSIZE ;[5]
neg cnt ;[6]
sub YL, cnt ;[7]
sbci YH, 0 ;[8]
ldi x2, 1<<USB_INTR_PENDING_BIT ;[9]
USB_STORE_PENDING(x2) ;[10] clear pending intr and check flag later. SE0 should be over.
ld token, y ;[11]
cpi token, USBPID_DATA0 ;[13]
breq handleData ;[14]
cpi token, USBPID_DATA1 ;[15]
breq handleData ;[16]
lds shift, usbDeviceAddr;[17]
ldd x2, y+1 ;[19] ADDR and 1 bit endpoint number
lsl x2 ;[21] shift out 1 bit endpoint number
cpse x2, shift ;[22]
rjmp ignorePacket ;[23]
/* only compute endpoint number in x3 if required later */
ldd x3, y+2 ;[24] endpoint number + crc
rol x3 ;[26] shift in LSB of endpoint
cpi token, USBPID_IN ;[27]
breq handleIn ;[28]
cpi token, USBPID_SETUP ;[29]
breq handleSetupOrOut ;[30]
cpi token, USBPID_OUT ;[31]
brne ignorePacket ;[32] must be ack, nak or whatever
; rjmp handleSetupOrOut ; fallthrough
;Setup and Out are followed by a data packet two bit times (16 cycles) after
;the end of SE0. The sync code allows up to 40 cycles delay from the start of
;the sync pattern until the first bit is sampled. That's a total of 56 cycles.
handleSetupOrOut: ;[32]
#if USB_CFG_IMPLEMENT_FN_WRITEOUT /* if we have data for endpoint != 0, set usbCurrentTok to address */
andi x3, 0xf ;[32]
breq storeTokenAndReturn ;[33]
mov token, x3 ;[34] indicate that this is endpoint x OUT
sts usbCurrentTok, token;[35]
POP_STANDARD ;[37] 12...16 cycles
sbrc YL, USB_INTR_PENDING_BIT;[50] check whether data is already arriving
rjmp waitForJ ;[51] save the pops and pushes -- a new interrupt is already pending
POP_RETI ;macro call
CRC_CLEANUP_AND_CHECK ; jumps to ignorePacket if CRC error
lds shift, usbCurrentTok;[18]
tst shift ;[20]
breq doReturn ;[21]
lds x2, usbRxLen ;[22]
tst x2 ;[24]
brne sendNakAndReti ;[25]
; 2006-03-11: The following two lines fix a problem where the device was not
; recognized if usbPoll() was called less frequently than once every 4 ms.
cpi cnt, 4 ;[26] zero sized data packets are status phase only -- ignore and ack
brmi sendAckAndReti ;[27] keep rx buffer clean -- we must not NAK next SETUP
sts usbCurrentDataToken, token ; store for checking by C code
sts usbRxLen, cnt ;[28] store received data, swap buffers
sts usbRxToken, shift ;[30]
lds x2, usbInputBufOffset;[32] swap buffers
ldi cnt, USB_BUFSIZE ;[34]
sub cnt, x2 ;[35]
sts usbInputBufOffset, cnt;[36] buffers now swapped
rjmp sendAckAndReti ;[38] 40 + 17 = 57 until SOP
;We don't send any data as long as the C code has not processed the current
;input data and potentially updated the output data. That's more efficient
;in terms of code size than clearing the tx buffers when a packet is received.
lds x1, usbRxLen ;[30]
cpi x1, 1 ;[32] negative values are flow control, 0 means "buffer free"
brge sendNakAndReti ;[33] unprocessed input packet?
ldi x1, USBPID_NAK ;[34] prepare value for usbTxLen
andi x3, 0xf ;[35] x3 contains endpoint
brne sendNakAndReti ;[36]
brne handleIn1 ;[36]
lds cnt, usbTxLen ;[37]
sbrc cnt, 4 ;[39] all handshake tokens have bit 4 set
rjmp sendCntAndReti ;[40] 42 + 16 = 58 until SOP
sts usbTxLen, x1 ;[41] x1 == USBPID_NAK from above
ldi YL, lo8(usbTxBuf) ;[43]
ldi YH, hi8(usbTxBuf) ;[44]
rjmp usbSendAndReti ;[45] 57 + 12 = 59 until SOP
; Comment about when to set usbTxLen to USBPID_NAK:
; We should set it back when we receive the ACK from the host. This would
; be simple to implement: One static variable which stores whether the last
; tx was for endpoint 0 or 1 and a compare in the receiver to distinguish the
; ACK. However, we set it back immediately when we send the package,
; assuming that no error occurs and the host sends an ACK. We save one byte
; RAM this way and avoid potential problems with endless retries. The rest of
; the driver assumes error-free transfers anyway.
#if !USB_CFG_SUPPRESS_INTR_CODE && USB_CFG_HAVE_INTRIN_ENDPOINT /* placed here due to relative jump range */
handleIn1: ;[38]
; 2006-06-10 as suggested by O.Tamura: support second INTR IN / BULK IN endpoint
cpi x3, USB_CFG_EP3_NUMBER;[38]
breq handleIn3 ;[39]
lds cnt, usbTxLen1 ;[40]
sbrc cnt, 4 ;[42] all handshake tokens have bit 4 set
rjmp sendCntAndReti ;[43] 47 + 16 = 63 until SOP
sts usbTxLen1, x1 ;[44] x1 == USBPID_NAK from above
ldi YL, lo8(usbTxBuf1) ;[46]
ldi YH, hi8(usbTxBuf1) ;[47]
rjmp usbSendAndReti ;[48] 50 + 12 = 62 until SOP
lds cnt, usbTxLen3 ;[41]
sbrc cnt, 4 ;[43]
rjmp sendCntAndReti ;[44] 49 + 16 = 65 until SOP
sts usbTxLen3, x1 ;[45] x1 == USBPID_NAK from above
ldi YL, lo8(usbTxBuf3) ;[47]
ldi YH, hi8(usbTxBuf3) ;[48]
rjmp usbSendAndReti ;[49] 51 + 12 = 63 until SOP