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Bit Level Variable Pointer In DB Block

Created by: Tonk at: 6/5/2012 5:18 PM (1 Replies)

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6/5/2012 5:18 PM	Rate (0)
Tonk Advanced Member Joined: 10/6/2006 Last visit: 9/4/2024 Posts: 54 Rating: (2)	Need help configuring a bit level varaible pointer within a DB. I have set up an array of 32 bits starting address is 158.0 I am monitoring an input and each time I see bit I want to set a bit within the array then I increment a counter which on the next cycle will set the next bit. I have no problem in creating the inital byte address but now I am struggling in trying to point to the individual bits from the start address. A "Tag_36" FP "Tag_32" JNB NTrig OPN "DB108_Hmi_Data" L "DB108_Hmi_Data".CentPointer T #Point L 0 *I T #temp2 L 316 +I SLD 2 LAR1 OPN "DB108_Hmi_Data" S DBX [ AR1 , P#0.0 ] L 1 L "DB108_Hmi_Data".CentPointer +I T "DB108_Hmi_Data".CentPointer NTrig: NOP 0

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6/16/2012 1:49 PM	Rate (0)
fritz Diamond Member Joined: 10/7/2005 Last visit: 10/10/2024 Posts: 3024 Rating: (1054)	Hello Tonk your calculation is a bit "odd" (e.g. "CentPointer" is multiplied with 0, start Byte address is nominated as 316 instead of 158 for which you then compensate by doing an SLD 2 instead of pointer typical SLD 3), so allow me to propose the following logic to you which shoulddo the job: A "Tag_36" FP "Tag_32" JNB NTrig LAR1 P#DBX 158.0 // point AR1 to start of bit field L "DB108_Hmi_Data".CentPointer // load bit indexvalue +AR1 // add to AR1 OPN "DB108_Hmi_Data" SET // RLO = 1(the above JNB takescare of this too, but this is "neater" S DBX [ AR1 , P#0.0 ] L "DB108_Hmi_Data".CentPointer + 1 // increment bit index value T "DB108_Hmi_Data".CentPointer NTrig: NOP 0 I hope this helps and have a look too at the FAQ below concerning all things indirect addressing related: STEP 7 -- Creating S7 programs -- Indirect Addressing
	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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