Studio 5000 Indirect Addressing

[RobWad]

Can someone explain to me the AND-16, and the AND 15 part of this indirect addressing? Thank you for any input.

B18[(N57_34 AND -16)/16].[N57_34 AND 15]

 

[rdrast]

They are masks.
15 = 0000 0000 0000 1111
-16 = 1111 1111 1111 0000


In one case, looking at only the low 4 bits of the word, in the other case, looking at only the high 12 bits of the word.

 

[RobWad]

Ahh thank you. It makes sense now. lol. This particular program was converted from a plc5 using the converter. Indirect logic is done differently in studio 5000 compared to the ole plc5 days. Thanks again.

 

[drbitboy]

Can someone explain to me the AND-16, and the AND 15 part of this indirect addressing? Thank you for any input.

B18[(N57_34 AND -16)/16].[N57_34 AND 15]

Sidebar: in some environments (e.g. MicroLogix 1xxx/RSLogix 500), that is equivalent to

B18[0].[N57_34]


OR


B18[0].[N57_34 AND 2147483647]

Also, the -16 should be positive and at most 2147482632 (0111 1111 1111 0000), because

1. I doubt B18 has 16Melements, or even 8Melements.
2. Dividing a negative number, which is what N57_34 will be if its MSBit is 1, by 16 will cause a fault, I think.