Subject:
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Re: NOTE 04/10/97 10:50:15
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 14 Apr 1997 19:38:43 GMT
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Original-From:
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Jeffrey Strauss Morehead <(morehead@)nomorespam(ece.utexas.edu)>
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Viewed:
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3893 times
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OK, I haven't looked at encoders.asm but if the following doesn't help
just send more questions.
On 10 Apr 1997, Ericson Mar wrote:
> Hi,
>
> Can someone help me understand encoders.asm?
>
> This is what I deduced from the code and I'm wondering if my guess is
> correct.
>
> 1. When TIC3 and TIC2 inputs are changed, an "interrupt" in execution
> occurs and and execution immediately jumps to the address stored at
> the location TIC3INT and TIC2INT. (In this case, Port0_ShaftInt,
> Port1_ShaftInt)
Sounds about right.
>
> 2. But for the interrupt to actually execute, TLFLG1 must allow it.
TCTL2 sets rising, falling, or both edge modes; TMSK1 arms interupts; IC
event sets the TFLG1 register.
> For TIC3 and TIC2, this must be true:
>
> TLFLG1 = %XXXXXXX1 -> TIC3 change causes an interrupt
> TLFLG1 = %XXXXXX1X -> TIC2 change causes an interrupt
correct
> TLFLG1 becomes %-------1 and %------1- on TIC3 and TIC2 changes
> respectively. So each bit must be turned off by the line
> BCLR TLFLG1,X %11111110 and
> BCLR TLFLG1,X %11111101 respectively,
correct
> otherwise, the interrupt will keept on executing after the very first
> change in state of TIC3 or TIC2, respectively.
> 3. TCLT2 stores a byte which when set to %00001111, makes the TIC3 and
> TIC2 interrupts happen when either inputs change state from 0 to 1.
> (What is at TCLT2 to make it interrupt on a 1 to 0 change?)
answer: TCTL2=0A =%00001010
TCTL2 bit 7 6 5 4 3 2 1 0
0 0 EDG1B EDG1A EDG2B EDG2A EDG3B EDG3A
PA2 mode PA1 mode PA0 mode
EDGxB EDGxA Input Capture Function
0 0 disabled
0 1 rising edge
1 0 falling edge
1 1 both rising and falling edges
Hope this helps
jm
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Message is in Reply To:
 | | NOTE 04/10/97 10:50:15
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| Hi, Can someone help me understand encoders.asm? This is what I deduced from the code and I'm wondering if my guess is correct. 1. When TIC3 and TIC2 inputs are changed, an "interrupt" in execution occurs and and execution immediately jumps to the (...) (30 years ago, 10-Apr-97, to lugnet.robotics.handyboard)
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