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NAME
BFEXTS -- Bit field signed extract
SYNOPSIS
BFEXTS <ea>{OFFSET:WIDTH},Dn (68020+)
No size specs.
FUNCTION
<ea> indicates source operand which a part of bits have to be
extracted and extended. Offset enables to locate first bit of field;
width specifies number of bits of this field. Field is extracted,
and extended to 32 bits by the MSB of the field. Result is stored
in the data register Dn.
Be careful, this instruction operates from MSB to LSB!!
FORMAT
<ea>
----------------------------------------=========================
|15 |14 |13 |12 |11 |10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|---|---|-----------|-----------|
| 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | MODE | REGISTER |
|---|-----------|---|-------------------|-----------------------|
| 0 | REGISTER |Do | OFFSET |Dw | WIDTH |
-----------------------------------------------------------------
If Do = 0->Field "OFFSET" contains an immediate value which represents
effective offset, value from 0 to 31.
If Do = 1->Field "OFFSET" indicates number of a data register (bits 9
and 10 of field cleared) which contains effective offset. Signed value
is represented on 32 bits., so it's extended from -2 EXP 31 to
(+2 EXP 31) -1.
If Dw = 0->field "WIDTH" contains an immediate value between 1 and 31
which indicates a width from 1 to 31 bits. A value of 0 indicates a
width of 32 bits.
If Dw = 1->field "WIDTH" indicates number of a data register (bits 3
and 4 of field cleared) which contains width of bit field. The value
modulo 32 can go from 1 to 31, indicating a width from 1 to 31 bits.
A value 0 indicates a width of 32 bits.
REGISTER
<ea> specifies destination, addressing modes are the followings:
--------------------------------- -------------------------------
|Addressing Mode|Mode| Register | |Addressing Mode|Mode|Register|
|-------------------------------| |-----------------------------|
| Dn |000 |N° reg. Dn| | Abs.W |111 | 000 |
|-------------------------------| |-----------------------------|
| An | - | - | | Abs.L |111 | 001 |
|-------------------------------| |-----------------------------|
| (An) |010 |N° reg. An| | (d16,PC) |111 | 010 |
|-------------------------------| |-----------------------------|
| (An)+ | - | - | | (d8,PC,Xi) |111 | 011 |
|-------------------------------| |-----------------------------|
| -(An) | - | - | | (bd,PC,Xi) |111 | 011 |
|-------------------------------| |-----------------------------|
| (d16,An) |101 |N° reg. An| |([bd,PC,Xi],od)|111 | 011 |
|-------------------------------| |-----------------------------|
| (d8,An,Xi) |110 |N° reg. An| |([bd,PC],Xi,od)|111 | 011 |
|-------------------------------| |-----------------------------|
| (bd,An,Xi) |110 |N° reg. An| | #data | - | - |
|-------------------------------| -------------------------------
|([bd,An,Xi]od) |110 |N° reg. An|
|-------------------------------|
|([bd,An],Xi,od)|110 |N° reg. An|
---------------------------------
RESULT
X - not affected
N - Set if MSB of field is set. Cleared otherwise.
Z - Set if all the bits of the field tested are zero.
Cleared otherwise.
V - Always cleared.
C - Always cleared.
SEE ALSO
BFEXTU