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thirsty
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Joined: 22/06/2016
Location: Australia
Posts: 34

Posted: 11:36pm 18 Jul 2016

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Hi Guys

So I've got this statement:

PORT(2,3,7,4,9,1)=&B10011001

What I'd like to do is conditionally change the first bit. I know I can AND/OR to change it but I'm not sure of the syntax.

I was thinking:

PORT(2,3,7,4,9,1) AND &B10000000

Would that work?

MicroBlocks

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Joined: 12/05/2012
Location: Thailand
Posts: 2209

Posted: 03:19am 19 Jul 2016

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A little reference:

[code]
Truth tables:

AND
=========
| 0 | 1
---------
0 | 0 | 0
---------
1 | 0 | 1

OR
=========
| 0 | 1
---------
0 | 0 | 1
---------
1 | 1 | 1
[/code]

AND only gives a 1 when both values are 1
OR only gives a 0 when both values are 0

This is for a single bit. So each single bit is used when AND or OR numbers.

If you want to make a single bit 1 then use OR with a bit 1 in that position.
If you want to make a single bit 0 then use AND with a bit 0 in that position.
Edited by MicroBlocks 2016-07-20

Microblocks. Build with logic.

thirsty
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Joined: 22/06/2016
Location: Australia
Posts: 34

Posted: 02:57pm 19 Jul 2016

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Thanks for that.

Do you know the syntax to do that in MMBasic?

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6269

Posted: 04:45pm 19 Jul 2016

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I think you can read the state of pins that have been set as outputs. If so,

currentstate = PORT(2,3,7,4,9,1) ' read the current settings
otherpins = currentstate AND &B01111111
toppin = currentstate AND &B10000000 ' value is 128 if set or zero if not set

'to set top pin leaving the other pins as they were
PORT(2,3,7,4,9,1)=&B10000000+otherpins
' to reset top pin
PORT(2,3,7,4,9,1)=&B00000000+otherpins ' or just PORT(2,3,7,4,9,1)=otherpins

If that doesn't work, you will need to keep a record of the settings of the other pins.

Jim

VK7JH
MMedit

robert.rozee
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Joined: 31/12/2012
Location: New Zealand
Posts: 2431

Posted: 07:37pm 19 Jul 2016

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i feel i must be missing something. what is wrong with:

pin(9) = 1

to set the top bit high,

pin(9) = 0

to clear the top bit, and,

pin(9) = not pin(9)

to flip the top bit?

(assuming the LAST pin specified in a PORT command is the topmost bit, just checked the manual and corrected post for this)

cheers,
rob :-)Edited by robert.rozee 2016-07-21

thirsty
Newbie

Joined: 22/06/2016
Location: Australia
Posts: 34

Posted: 08:52pm 19 Jul 2016

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Actually Rob you are quite right - I think I was just trying to be a bit too clever :) and focusing on the need to change the pattern over the entire port range. The bit I'm trying to turn on/off is indeed on a particular pin and I can just turn it on or off by using the Pin command.

Thanks again all.

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