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???
04/13/08 12:24
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 		 #153184 - It is an absolute paged call...
Responding to: ???'s previous message
The instruction is fully described here: http://www.8052.com/51acall.phtml

When the instruction executes the two bytes are fetched as follows:

PC -> ACALL Opcode
PC++ -> ACALL Address Operand
PC++ -> Next Instruction

The destination address of the call has the program counter set as:

PC<15:11> <- PC<15:11> ; From next instruction address
PC<10:8> <- Opcode<7:5> ; Page address from opcode
PC<7:0> <- Address<7:0> ; Page offset from operand

Michael Karas


List of 42 messages in thread
TopicAuthorDate
Problem with ACALL instruction            01/01/70 00:00      
   It is an absolute paged call...            01/01/70 00:00      
      my question is different            01/01/70 00:00      
         The Opcode is Selected...            01/01/70 00:00      
   not using an assembler?            01/01/70 00:00      
      still confused...            01/01/70 00:00      
         Not possible, use LCALL            01/01/70 00:00      
            Why should anyone WANT to know the hex            01/01/70 00:00      
               he'd want to know it because ...            01/01/70 00:00      
                  Unnecessary complication            01/01/70 00:00      
         compiler results error            01/01/70 00:00      
            There is no compiler involved. Just an assembler.            01/01/70 00:00      
         3 top bits of 11-bit address            01/01/70 00:00      
            only good for calls within the same 2K block            01/01/70 00:00      
            one more question...            01/01/70 00:00      
               Read your instruction set            01/01/70 00:00      
                  i am making an assembler.            01/01/70 00:00      
                     Now I understand. Far more interesting.            01/01/70 00:00      
                        Absolute Assembler            01/01/70 00:00      
                           what is an absolute assembler            01/01/70 00:00      
                              Which do you love.            01/01/70 00:00      
                                 actually I didn't            01/01/70 00:00      
                                    Linking assemblers are more complicated            01/01/70 00:00      
                     why not?            01/01/70 00:00      
               ajmp            01/01/70 00:00      
                  Reconsider Robert....            01/01/70 00:00      
                     positive offset...            01/01/70 00:00      
                        No !!!            01/01/70 00:00      
                           let's try this way            01/01/70 00:00      
                              abc?            01/01/70 00:00      
                                 I do not know how micro            01/01/70 00:00      
                                    can any1 tell abc??            01/01/70 00:00      
                                       As easy as 'abc'            01/01/70 00:00      
                                       How to get ABC            01/01/70 00:00      
                           whats the operand here?            01/01/70 00:00      
                              neither!!!!            01/01/70 00:00      
                                 is that an error?            01/01/70 00:00      
                                    error, not necessarily, but ..            01/01/70 00:00      
                                    it is not an error, but it is poor practice            01/01/70 00:00      
                        Not offset            01/01/70 00:00      
                           Oops, I was wrong earlier            01/01/70 00:00      
   Problem solved            01/01/70 00:00      

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