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authorChristian Starkjohann <cs+github@obdev.at>2009-08-06 09:49:18 +0000
committerChristian Starkjohann <cs+github@obdev.at>2009-08-06 09:49:18 +0000
commitb6a66c5058b8f646f9544582da8c330887ab6bd7 (patch)
tree0110791956cb1220154616c4bd5f275fa3330f1b /usbdrv/usbdrvasm128.inc
parentd988c3906ece23375bee7cc56cc8633761577baf (diff)
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- fixed SE0 check: The check was done in the middle between bit 0 and 1,
exactly where the data lines can change. We now check only if both, bits 0 and 1 have been read as 0 on D-.
Diffstat (limited to 'usbdrv/usbdrvasm128.inc')
-rw-r--r--usbdrv/usbdrvasm128.inc30
1 files changed, 15 insertions, 15 deletions
diff --git a/usbdrv/usbdrvasm128.inc b/usbdrv/usbdrvasm128.inc
index c98d363..ff23a22 100644
--- a/usbdrv/usbdrvasm128.inc
+++ b/usbdrv/usbdrvasm128.inc
@@ -31,8 +31,9 @@ limitations:
They typical range is 14.5 MHz and most AVRs can actually reach this rate.
(2) Writing EEPROM and Flash may be unreliable (short data lifetime) since
the write procedure is timed from the RC oscillator.
-(3) End Of Packet detection is between bit 0 and bit 1 where the EOP condition
-may not be reliable when a hub is used. It should be in bit 1.
+(3) End Of Packet detection (SE0) should be in bit 1, bit it is only checked
+if bits 0 and 1 both read as 0 on D- and D+ read as 0 in the middle. This may
+cause problems with old hubs which delay SE0 by up to one cycle.
(4) Code size is much larger than that of the other modules.
Since almost all of this code is timing critical, don't change unless you
@@ -225,11 +226,11 @@ bit0IsClr:
in phase, USBIN ;[06] <- phase (one cycle too late)
ori shift, 1 << 0 ;[07]
bit1AfterClr:
- andi phase, USBMASK ;[08]
+ andi shift, ~(7 << 1) ;[08] compensated by "ori shift, 1<<1" if bit1IsSet
ifioset USBIN, USBMINUS ;[09] <--- sample 1
rjmp bit1IsSet ;[10]
- breq jumpToSe0AndStore ;[11]
- andi shift, ~(7 << 1) ;[12]
+ ifrclr phase, USBPLUS ;[11] if D- was 0 in bits 0 AND 1 and D+ was 0 in between, we have SE0
+ rjmp se0AndStore ;[12]
in phase, USBIN ;[13] <- phase
breq unstuff1c ;[14]
rjmp bit2AfterClr ;[15]
@@ -391,25 +392,24 @@ bit0IsSet:
in phase, USBIN ;[06] <- phase (one cycle too late)
ori shift, 1 << 0 ;[07]
bit1AfterSet:
- andi phase, USBMASK ;[08]
+ andi shift, ~(7 << 1) ;[08] compensated by "ori shift, 1<<1" if bit1IsClr
ifioclr USBIN, USBMINUS ;[09] <--- sample 1
rjmp bit1IsClr ;[10]
- andi shift, ~(7 << 1) ;[11]
- breq unstuff1s ;[12]
- in phase, USBIN ;[13] <- phase
- nop ;[14]
+ breq unstuff1s ;[11]
+ nop2 ;[12] do not check for SE0 if bit 0 was 1
+ in phase, USBIN ;[14] <- phase (one cycle too late)
rjmp bit2AfterSet ;[15]
unstuff1s:
- in phase, USBIN ;[14] <- phase (one cycle too late)
- andi fix, ~(1 << 1) ;[15]
- nop2 ;[08]
+ in phase, USBIN ;[13] <- phase
+ andi fix, ~(1 << 1) ;[14]
+ lpm ;[07]
nop2 ;[10]
bit1IsClr:
ifrset phase, USBMINUS ;[12] check phase only if D- changed
lpm ;[13]
in phase, USBIN ;[14] <- phase (one cycle too late)
- breq se0AndStore ;[15] if we come from unstuff1s, Z bit is never set
- ori shift, 1 << 1 ;[16]
+ ori shift, 1 << 1 ;[15]
+ nop ;[16]
bit2AfterClr:
ifioset USBIN, USBMINUS ;[17] <--- sample 2
rjmp bit2IsSet ;[18]