#---------------------------------------- # Purpose - Create some $BIT variables # Create $K and $M variables # and some bit field extraction variables. # Creat helper variables ... # BIT0.. BIT31 for { set x 0 } { $x < 32 } { set x [expr $x + 1]} { set vn [format "BIT%d" $x] global $vn set $vn [expr (1 << $x)] } # Create K bytes values # __1K ... to __2048K for { set x 1 } { $x < 2048 } { set x [expr $x * 2]} { set vn [format "__%dK" $x] global $vn set $vn [expr (1024 * $x)] } # Create M bytes values # __1M ... to __2048K for { set x 1 } { $x < 2048 } { set x [expr $x * 2]} { set vn [format "__%dM" $x] global $vn set $vn [expr (1024 * 1024 * $x)] } proc create_mask { MSB LSB } { return [expr (((1 << ($MSB - $LSB + 1))-1) << $LSB)] } # Cut Bits $MSB to $LSB out of this value. # Example: % format "0x%08x" [extract_bitfield 0x12345678 27 16] # Result: 0x02340000 proc extract_bitfield { VALUE MSB LSB } { return [expr [create_mask $MSB $LSB] & $VALUE] } # Cut bits $MSB to $LSB out of this value # and shift (normalize) them down to bit 0. # # Example: % format "0x%08x" [normalize_bitfield 0x12345678 27 16] # Result: 0x00000234 # proc normalize_bitfield { VALUE MSB LSB } { return [expr [extract_bitfield $VALUE $MSB $LSB ] >> $LSB] } proc show_normalize_bitfield { VALUE MSB LSB } { set m [create_mask $MSB $LSB] set mr [expr $VALUE & $m] set sr [expr $mr >> $LSB] echo [format "((0x%08x & 0x%08x) -> 0x%08x) >> %2d => (0x%x) %5d " $VALUE $m $mr $LSB $sr $sr] return $sr }