Freescale Semiconductor StarCore SC140 - Manual (Page 563)

MAX2VIT
SC140 DSP Core Reference Manual A-249
MAX2VIT
MAX2
MAX2VIT
for Viterbi Kernel (DALU)
Description
These operations independently compare the 16-bit contents of the HP and LP of a data register pair to find
the larger value. They copy the larger value to the corresponding portion in the second data register and set
or clear Viterbi flags (VF0–VF3 in SR) to indicate which portions are larger. The HP and LP of the two
registers are compared separately as 16-bit signed values and the Viterbi flags are set or cleared
accordingly. These instructions are similar to MAX2, except they also set Viterbi flags. The MAX2VIT
instructions are intended to optimize implementation of the Viterbi decoder algorithm. The MAX2VIT
instruction is used with conjunction with the VSL instruction (see page A-423).
Status and Conditions that Affect Instruction
None.
Operation Assembler Syntax
If Da.L
> Db.L, then 0 → VFn, Da.L → Db.L
else 1
→ VFn
MAX2VIT Da,Db
Da Db VFn
D4.L D2.L VF0
D4.H D2.H VF1
D0.L D6.L VF2
D0.H D6.H VF3
D12.L D10.L VF0
D12.H D10.H VF1
D8.L D14.L VF2
D8.H D14.H VF3
MAX2VIT Da,Db
For the low portion comparison, the instruction clears VFn (n=0, 2) if the LP of Da is greater than the LP of
Db. It then copies the contents of the LP of Da to the LP of Db. It sets VFn (n=0, 2) if the LP of Da is not
greater than the LP of Db. For the high portion comparison, this instruction clears VFn (n=1, 3) if the HP of
Da is greater than the HP of Db. It then copies the contents of the HP of Da to the HP of Db. It sets VFn
(n=1, 3) if the HP of Da is not greater than the HP of Db. The high bank of registers can also be used: D12
and D8 substituted for Da, and D10 and D14 substituted for Db. The encoding for the substitution is done
with a prefix.