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Pointer Query

Created by: Yokesh Kumar S at: 7/22/2011 7:45 AM (3 Replies)

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7/22/2011 7:45 AM	Rate (0)
Yokesh Kumar S Regular Member Joined: 9/3/2009 Last visit: 8/9/2022 Posts: 11 Rating: (0)	Dear All, i refered one old program, in that they have used a pointer but i am not understanding how it will work L P#P0.0, by loading only offset from which address it will take the value, please find the attached picture. Attachment Pointer.JPG (66 Downloads)

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7/22/2011 8:23 AM	Rate (0)
Aret Posts: 2348 Rating: (259)	Actually there is START_ADDRESS, which contains proper pointer. By these instructions L P#P0.0 OD you just add area identifier to pointer.
Aret Posts: 2348 Rating: (259)
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7/22/2011 8:31 AM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 6/2/2023 Posts: 6803 Rating: (1345)	Yokesh Kumar S Dear All, i refered one old program, in that they have used a pointer but i am not understanding how it will work L P#P0.0, by loading only offset from which address it will take the value, please find the attached picture. First check this: Step 7 Indirect addressing FAQ & Examples collection Programming a Loop with Indirect Addressing Averaging via ANY pointer Pointer transfer to a function Also your codes with comments: [code]L #SLOT_NO L 2 I L 20 +I //Value calculated according to the formula L L#8 D // shift to left 3 bits to create byte address T #STR_ADDR //transfer the created pointer //to an address L P#P0.0 // load format of a pointer OD //OR doubleword by calculated value T #STR_ADDR [/code] Regards
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7/22/2011 9:15 AM	Rate (0)
Aret Posts: 2348 Rating: (259)	I'm slightly disagree with hdhosseini L P#P0.0 means L DW#16#80000000, i.e. by doing this you add I/O area identifier to pointer, calculated before. So on using that pointer you will work with IO area. Such code L P#0.0 OD is equal to NOPx2 :^) Please mention the difference between P#0.0 and P#P0.0
Aret Posts: 2348 Rating: (259)	Last edited by: Aret at: 7/22/2011 9:17 AM
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This contribution was helpful to 2 thankful Users fritz hdhosseini

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