Step7 Basic operations, program blocks - DCE FEL ČVUT v Praze
Step7 Basic operations, program blocks - DCE FEL ČVUT v Praze
Step7 Basic operations, program blocks - DCE FEL ČVUT v Praze
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• Pointer ‐ 32 bits<br />
• Address registers AR1, AR2<br />
• Indirect addressing<br />
– Memory‐based … T QW[MD12] –write an output word to an address<br />
given by the value of MD12<br />
– Register‐based … T QW[AR1,P#2.0] –write an output word to an<br />
address given by the sum of address register AR1 and 2<br />
• Operations with address registers<br />
– LAR1, LAR2 … load ACCU1 to address register<br />
– LAR1 MD12, LAR1 P#M0.0 … load value to address reg.<br />
– TAR1, TAR2 … transfer value from address register<br />
IMPORTANT<br />
Pointer to address area: P#M0.0 BYTE 20, P#DB1.DBX0.0 BYTE 20<br />
• Area and out‐of‐area addressing<br />
Indirect addressing<br />
A space in the<br />
DB must be<br />
allocated, i.e.<br />
ARRAY<br />
Indirect addressing<br />
– Area … L MW[AR1,P#0.0] –the address space is part of the operand<br />
– Out‐of‐area … L W[AR1,P#0.0] –the address space is given by the<br />
address register<br />
• Examples<br />
– Memory indirect addressing with the area pointer<br />
L P#30.0<br />
T MD12<br />
L MW[MD12]<br />
– Memory indirect addressing with a value –to address counters, timers<br />
and <strong>blocks</strong><br />
L 133<br />
T MW20<br />
OPN DB[MW20]<br />
SE T[MW20]<br />
3.10.2012<br />
9
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