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COMPARE instruction with Data Type BYTE

Created by: jonp at: 3/9/2008 9:35 AM (4 Replies)

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3/9/2008 9:35 AM	Rate (0)
jonp Posts: 4 Rating: (0)	It seems it is not possible tocompare byte to integerwith theCOMP instruction (except within GRAPH 7, when it works!!). You need to move the source byte to a scratch word, thencompare the scratch word to the integer. Is there an easier way? Secondly, if you use the MOVE instruction with data type REAL, the value gets screwed up. You have to use the ADD_R instruction instead. What's that all about? Finally- all those different timers! But none are retentitive - ie timer stops without resetting when enable goes low,then carries on when enable goes high. I've made my own with a 1 second timer and an integer word - is there an easier way?
jonp Posts: 4 Rating: (0)	Last edited by: jonp at: 09.03.2008 09:51
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3/9/2008 11:46 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 12/11/2024 Posts: 12302 Rating: (2692)	Hello jonp; In Step 7, LAD and FBD maintain "type checking" to ensure comparison levels; you can either disable type checking, or use STL to do the comparison; for example, thisshould work. L #bytevalue_1 L #bytevalue_2 <I S I0.0 For the retentive timer question , FC80 (in the TI-S7 converting blocks library) is a retentive TON. You could also look at the code in this document, to generate a retentive timer to your specific needs: http://support.automation.siemens.com/WW/view/en/858026 Hope this helps, Daniel chartier

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1/29/2013 12:56 PM	Rate (0)
JoelR Regular Member Joined: 1/22/2013 Last visit: 2/28/2022 Posts: 9 Rating: (0)	I realise this is a five year old post, but since I found it relevant: With the suggestion above: L #SymbolicByteTag1 L #SymbolicByteTag2 >I S #bit Does this mean that the ACC1 & ACC2 areas that are compared but not loaded.. are all zeroes? I know that the accumulators are 32-bit in size, but usually you dont adress more than you have loaded them with... So I guess the core of the question is: If you load an accumulator with less than 32-bit, what does the rest of the space consist of?
	Last edited by: JoelR at: 1/29/2013 12:57 PM
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1/30/2013 1:52 AM	Rate (1)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 12/12/2024 Posts: 3029 Rating: (1057)	JoelR So I guess the core of the question is: If you load an accumulator with less than 32-bit, what does the rest of the space consist of? Hello JoelR the simple answer is that it consists of zeros and the attached pic has more on this (taken striaght from the inbuilt Step7 <F1> context sensitivehelp onthe "L" instruction). Attachment STL Load instruction effect on accu1.jpg (1218 Downloads)
	Last edited by: fritz at: 1/30/2013 1:54 AM Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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This contribution was helpful to 2 thankful Users Cybertronic JoelR

4/1/2014 9:48 AM	Rate (0)
CS Moderator Moderator Joined: 9/1/2005 Last visit: 12/12/2024 Posts: 4114 Rating: (195)	follow up question published by AlfredoSAis split to a seperate thread with the subject COMPARE "Byte zero" can be B#16#00 (Exadecimal) or B#16#30 (Char) Best regards CS Moderator
	My Forum is the place to personalize your profile, track your topics, and maintain content that interests you. Best regards CS Moderator
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