How Z flag of (MINS, MAXS, MIN, MAX) and C Flag of (ADDABS, SUBABS) work?
paulchainkang
Posts: 10
Hello all,
I found something interesting when test the Propeller Assembly Instructions.
1. Z Flag of MINS, MAXS, MIN and MAX
The Instruction set of Core Docs.pdf says Z out is "D=S". But my test shows
mins $55, $55 => Z= 0
maxs $55, $55 => Z= 0
min· $55, $55 => Z= 0
max· $55, $55 => Z= 0
I though all the Z flags should be 1.
2. C Flag of ADDABS and SUBABS
The Instruction set of Core Docs.pdf says·C out is "Unsigned Carry" for ADDABS·and is "Unsigned Borrow" for SUBABS. But my test shows
addabs $00000055,-$AA => C= 1 (a)
addabs $FFFFFFFF,-$01 => C= 0 (b)
subabs $000000AA,-$55 => C= 1 (c)
I though in case (a) and (c) the C Flags should be 0. The -$AA and -$55 after ABS are $AA and $55. They should not cause Unsigned Carry·in the addition and substration.
In case·(b), I thought the addition of $FFFFFFFF and $1 (after ABS) should cause Carry. But the C flag is 0.
Attached is my test program. It would send the results to RS232 with 19200 8N1.
Any help is appreciated.
Paul
I found something interesting when test the Propeller Assembly Instructions.
1. Z Flag of MINS, MAXS, MIN and MAX
The Instruction set of Core Docs.pdf says Z out is "D=S". But my test shows
mins $55, $55 => Z= 0
maxs $55, $55 => Z= 0
min· $55, $55 => Z= 0
max· $55, $55 => Z= 0
I though all the Z flags should be 1.
2. C Flag of ADDABS and SUBABS
The Instruction set of Core Docs.pdf says·C out is "Unsigned Carry" for ADDABS·and is "Unsigned Borrow" for SUBABS. But my test shows
addabs $00000055,-$AA => C= 1 (a)
addabs $FFFFFFFF,-$01 => C= 0 (b)
subabs $000000AA,-$55 => C= 1 (c)
I though in case (a) and (c) the C Flags should be 0. The -$AA and -$55 after ABS are $AA and $55. They should not cause Unsigned Carry·in the addition and substration.
In case·(b), I thought the addition of $FFFFFFFF and $1 (after ABS) should cause Carry. But the C flag is 0.
Attached is my test program. It would send the results to RS232 with 19200 8N1.
Any help is appreciated.
Paul
