Propeller Manual

3: Assembly Language Reference
Propeller Manual v1.1 · Page 253
ADDS Truth Table:
In Out
Destination Source Z C Effects Destination Z C
$FFFF_FFFF; -1 $0000_0001; 1 - -
wz wc
$0000_0000; 0 1 0
$FFFF_FFFF; -1 $0000_0002; 2 - -
wz wc
$0000_0001; 1 0 0
$0000_0001; 1 $FFFF_FFFF; -1 - -
wz wc
$0000_0000; 0 1 0
$0000_0001; 1 $FFFF_FFFE; -2 - -
wz wc
$FFFF_FFFF; -1 0 0
$7FFF_FFFE; 2,147,483,646 $0000_0001; 1 - -
wz wc
$7FFF_FFFF; 2,147,483,647 0 0
$7FFF_FFFE; 2,147,483,646 $0000_0002; 2 - -
wz wc
$8000_0000; -2,147,483,648 0 1
$8000_0001; -2,147,483,647 $FFFF_FFFF; -1 - -
wz wc
$8000_0000; -2,147,483,648 0 0
$8000_0001; -2,147,483,647 $FFFF_FFFE; -2 - -
wz wc
$7FFF_FFFF; 2,147,483,647 0 1
In the
ADDS truth table there are eight data rows grouped into four pairs. Each group exploits
a different boundary condition. The first five columns of each row indicate the inputs to the
instruction and the last three columns show the resulting outputs.
• The first pair of data rows demonstrates a simple signed addition (-1 + 1) that results
in zero (z flag set) and also an example (-1 + 2) that results in non-zero (Z flag clear).
• The second pair of rows shows the same concept but with inverted signs on the
values; (1 + -1) and (1 + -2).
• The third pair of rows demonstrates an addition near the highest signed integer
boundary (2,147,482,646 + 1) followed by another that crosses that boundary
(2,147,482,646 + 2) resulting in a signed overflow (C flag set).
• The fourth pair of rows shows the same concept but approaching and crossing the
signed integer boundary from the negative side, also resulting in a signed overflow
(C flag set).
Note that an instruction’s destination field actually contains the address to a register that
holds the desired operand value, and the source field is often encoded similarly, but the truth
tables always simplify this detail by only showing the desired operand value itself for each
source and destination.
Propeller Assembly Instruction Master Table
A master table for all Propeller Assembly instructions is provided on the next two pages. In
this table, D and S refer to the instructions’ destination and source fields, also known as
d-field and s-field, respectively. Please be sure to read the notes on the page that follows the
table.