BS1 newbie questions

JackPollack

Hi, am a newbie and have several BS1 questions:

1. I am using· lookup to build a table of binary coded decimal data
eg:
27 Really represents 010 (binary 2) and 111 (binary 7)
54 Really represents 101 (binary 5) and·010 (binary 4)

If b0 is my BDC number (54)
I am unsing· b0/10//10·to get digit 1 and· b0//10 to get digit 2

How can I output to 3 specific bits based on my decimal number without effecting the other bits?

2. I screwed up on the bit order. I used ABCD... instad of ...DCBA. So if there is a simple answer to question 1 (I am thinking some type of bit mask, but don't really know how to create it) I think that the numbers I output are going to need to be flipped.

Sorry if this is hard to understand, but I am REALLY CONFUSED.

Thanks for your help

JackPollack

I want to output parallel

eg

00 111 111
unused bits Digit 1 Digit2

But remember for me the unused bits are pin 6 & 7

Jon Williams

Why are you only using three bits? BCD numbers use four bits, and you can't represent the digits 8 and 9 without the fourth bit.

How do you want to do your output? If, for example you were going to use P0-P3 for the one's digit, and P4-P7 for the ten's digit, you could do this:

Pins = decVal / 10 * 16
Pins = decVal // 10 | Pins

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Jon Williams
Applications Engineer, Parallax
Dallas Office

JackPollack

My output is driving 2 seperate demultiplexers that only count to 7 (3 bits)

>How do you want to do your output?

I want bits 5,4,3 to be digit 1 (remember bit 5 is my 1 bit)
I want bits 2,1,0 to be digit 2 (2 is my 1 bit for this pair)

Jon Williams

You can use LOOKUP to correct the bits.

d1 = decVal / 10 
LOOKUP d1, (%000, %100, %010, %110, %001, %101, %011, %111), d1 
Pins = d1 * 8 
d2 = decVal // 10 
LOOKUP d2, (%000, %100, %010, %110, %001, %101, %011, %111), d2 
Pins = Pins | d2

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Jon Williams
Applications Engineer, Parallax
Dallas Office

JackPollack

I think that did the trick :-)

Thanks, and have a nice holiday.