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problem with understanding of Accu1 and Accu2

Created by: Andy312 at: 4/3/2012 11:57 AM (7 Replies)

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4/3/2012 11:57 AM	Rate (0)
Andy312 Experienced Member Joined: 9/16/2008 Last visit: 11/16/2022 Posts: 35 Rating: (0)	Hi there, I encountered an problem regarding a piece of code that I have on my assemblying line. The code isbelow and in the right part it is what Iunderstood: L 254 ;Load in Accu1 254 L#DestNum;Load thevalue of DestNum(wich is 1,2,3 or 4) in Accu1 and 254 goes in Accu2 + -1 ;the value of Accu1 will be DestNum-1 -D;the result of Accu1 is: 254-(DestNum-1) L B#16#1 ;the Accu1 will be 1 and Accu2 will be 254-(DestNum-1) SPM EHEr ;jumps if result of Accu1 is less than 0. My question is :1-If I load 1 right before 'SPM EHEr' the result will never be less than 0,so than what is the point of this jump instruction. Thank you very much for helping me! Best regards Andrei

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4/3/2012 12:30 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 5/2/2023 Posts: 2957 Rating: (242)	Hi, Jump instructions check status bits and you will not change status bit with just load instruction. You need to make comparine or some arithmetic instruction to influeance status bits. Look more in Step-7 STL help for arithmetic/compare/load instructions.
	Best regards, Darius
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4/3/2012 12:37 PM	Rate (0)
Andy312 Experienced Member Joined: 9/16/2008 Last visit: 11/16/2022 Posts: 35 Rating: (0)	Yes Darius, But in the help file of SPM ,it says that the instruction is made only if the result of the Accu1 is <1. And as I said Accu1=1 in my previous instruction. Thanks a lot!

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4/3/2012 12:47 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 5/2/2023 Posts: 2957 Rating: (242)	Well I can't find any jump instruction with name SPM and whch jumps if ACCU1 < 1. What is that instruction anyways ?
	Best regards, Darius
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4/3/2012 12:53 PM	Rate (0)
Andy312 Experienced Member Joined: 9/16/2008 Last visit: 11/16/2022 Posts: 35 Rating: (0)	Yes, Sorry!The right jump instruction is JM.It was weitten in french!So consider SPM as JM. Best regards! Andrei

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4/3/2012 1:10 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 5/2/2023 Posts: 2957 Rating: (242)	thanks for correction. So here it goes from help system: "If status bits CC 1 = 0 and CC 0 = 1, JM <jump label> (jump if result < 0) interrupts the linear program scan and jumps to a jump destination." And you will not change CC 1 or CC 0 with load instruction. You need arithmetic or compare instruction for that. Again, see help for load instruction and the let's say for -D instruction and you will see by yourself.
	Best regards, Darius
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4/3/2012 1:33 PM	Rate (0)
Andy312 Experienced Member Joined: 9/16/2008 Last visit: 11/16/2022 Posts: 35 Rating: (0)	Hi, Thank you a lot Darius! Best regards! Andrei

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4/3/2012 1:43 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 5/2/2023 Posts: 2957 Rating: (242)	You're welcome
	Best regards, Darius
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