diff options
Diffstat (limited to 'usbdrv/usbdrvasm15.inc')
| -rw-r--r-- | usbdrv/usbdrvasm15.inc | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/usbdrv/usbdrvasm15.inc b/usbdrv/usbdrvasm15.inc index 689d2a3..a315eae 100644 --- a/usbdrv/usbdrvasm15.inc +++ b/usbdrv/usbdrvasm15.inc @@ -43,11 +43,14 @@ 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) -;------------------------------------------------------------------------------- -waitForJ: ;- - sbis USBIN, USBMINUS ;1 <-- sample: wait for D- == 1 - rjmp waitForJ ;2 +;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: + sbic USBIN, USBMINUS + rjmp waitForK + inc YL + 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. |