1 #----------------------------------------
2 # Purpose - Create some $BIT variables
3 # Create $K and $M variables
4 # and some bit field extraction variables.
5 # Creat helper variables ...
8 for { set x 0 } { $x < 32 } { set x [expr $x + 1]} {
9 set vn [format "BIT%d" $x]
10 set $vn [expr (1 << $x)]
15 # Create K bytes values
17 for { set x 1 } { $x < 2048 } { set x [expr $x * 2]} {
18 set vn [format "__%dK" $x]
19 set $vn [expr (1024 * $x)]
23 # Create M bytes values
25 for { set x 1 } { $x < 2048 } { set x [expr $x * 2]} {
26 set vn [format "__%dM" $x]
27 set $vn [expr (1024 * 1024 * $x)]
31 proc create_mask { MSB LSB } {
32 return [expr (((1 << ($MSB - $LSB + 1))-1) << $LSB)]
36 # Cut Bits $MSB to $LSB out of this value.
37 # Example: % format "0x%08x" [extract_bitfield 0x12345678 27 16]
40 proc extract_bitfield { VALUE MSB LSB } {
41 return [expr [create_mask $MSB $LSB] & $VALUE]
45 # Cut bits $MSB to $LSB out of this value
46 # and shift (normalize) them down to bit 0.
48 # Example: % format "0x%08x" [normalize_bitfield 0x12345678 27 16]
51 proc normalize_bitfield { VALUE MSB LSB } {
52 return [expr [extract_bitfield $VALUE $MSB $LSB ] >> $LSB]
55 proc show_normalize_bitfield { VALUE MSB LSB } {
56 set m [create_mask $MSB $LSB]
57 set mr [expr $VALUE & $m]
58 set sr [expr $mr >> $LSB]
59 puts [format "((0x%08x & 0x%08x) -> 0x%08x) >> %2d => (0x%x) %5d " $VALUE $m $mr $LSB $sr $sr]