Propeller Manual

MOVS – Assembly Language Reference
MOVS
Instruction: Set a register’s source field to a value.
MOVS Destination, 〈#〉 Value
Result: Value is stored in Destination’ s-field (bits 8..0).
•
Destination (d-field) is the register whose source field (bits 8..0) is set to Value’s
value.
•
Value (s-field) is a register or a 9-bit literal whose value is stored into Destination’s
source field.
Opcode Table:
–INSTR– ZCRI –CON– –DEST– –SRC– Z Result C Result Result Clocks
010100 001i 1111 ddddddddd sssssssss
Result = 0 --- Written 4
Concise Truth Table:
In Out
Destination Source Z C Effects Destination Z C
$0000_0000; 0 $0000_0000; 0 - -
wz wc
$0000_0000; 0 1 0
$0000_0000; 0 $0000_01FF; 511 - -
wz wc
$0000_01FF; 511 0 1
$FFFF_FFFF; -1 $0000_01FF; 511 - -
wz wc
$FFFF_FFFF; -1 0 0
$FFFF_FFFF; -1 $0000_0000; 0 - -
wz wc
$FFFF_FE00; -512 0 0
Explanation
MOVS copies the 9-bit value of Value into Destination’s source field (s-field) bits 8..0.
Destination’s other bits are left unchanged. This instruction is handy for setting certain
registers like
CTRA and VCFG, and for updating the source field of instructions in self-
modifying code.
For self-modifying code, ensure that at least one other instruction is executed between a
MOVS
instruction and the target instruction that MOVS modifies. This gives the cog time to write
MOVS’s result before it fetches the target instruction for execution; otherwise, the as-yet-
unmodified version of the target instruction would be fetched and executed.
If the
WZ effect is specified, the Z flag is set (1) if Value equals zero. The result is written to
Destination unless the
NR effect is specified.
Page 314 · Propeller Manual v1.1