diff options
Diffstat (limited to 'usbdrv/usbdrvasm20.inc')
| -rw-r--r-- | usbdrv/usbdrvasm20.inc | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/usbdrv/usbdrvasm20.inc b/usbdrv/usbdrvasm20.inc index 2d4be52..ebe14e2 100644 --- a/usbdrv/usbdrvasm20.inc +++ b/usbdrv/usbdrvasm20.inc @@ -57,10 +57,14 @@ USB_INTR_VECTOR: ;---------------------------------------------------------------------------- ;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 -;first part has no timeout because it waits for IDLE or SE1 (== disconnected) +;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: - sbis USBIN, USBMINUS ;[-21] wait for D- == 1 - rjmp waitForJ + sbic USBIN, USBMINUS + rjmp waitForK + inc YL + 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 ;[-19] |