[Coco] 6809 CC Reg Overflow bit

[Salvador Garcia]

 Thanks all! Your posts are appreciated.

I suspected that it could be an error, but wondered how it could have gotten through the edit process. I have not looked for an errata for this book.

Salvador


    On Tuesday, November 6, 2018, 4:49:21 PM CST, William Astle <lost at l-w.ca> wrote:  
 
 On 2018-11-06 3:14 p.m., Salvador Garcia via Coco wrote:
> Hi all. I am reading William Barden's Assembly Language for the Color Computer and on the bottom of page 57 he presents the following code <snipped>:
> 
> LDA #100
> ADDA #100   100 + 100 = 200  = V!
> 
> Then on the second paragraph below the code he states:
> 
> 
> "... The first ADD added an immediate 100 to the 100 in the A register for a result of 200. This is an overflow condition, and the V Condition Code should have been set to a 0, indicating no overflow:"
> 
> If the V Condition Code is set to a 1 to indicate overflow, and the 100 + 100 op caused an overflow, why is he saying that the V Condition code is set to a 0?
> 
> Am I missing something? As always, thanks! Salvador

The text is in error. V will be set after that instruction sequence.

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