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