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NAME
ASL, ASR -- Arithmetic shift left and arithmetic shift right
SYNOPSIS
ASd Dx,Dy
ASd #<data>,Dy
ASd <ea>
where d is direction, L or R
Size = (Byte, Word, Long)
FUNCTION
Performs an arithmetic shifting bit operation in the indicated
direction, with an immediate data, or with a data register.
If you shift address contents, you only can do ONE shift, and
your operand is ONE word exclusively.
ASL: <--
C <------ OPERAND <--- 0
|
|
X <---'
ASR: -->
.---> OPERAND ------> C
| T |
| | |
`----' `---> X
FORMAT
In the case of the shifting of a register:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-----------------------------------------------------------------
|15 |14 |13 |12 |11 |10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|-----------|---|-------|---|---|---|-----------|
| 1 | 1 | 1 | 0 | NUMBER/ |dr | SIZE |i/r| 0 | 0 | REGISTER |
| | | | | REGISTER | | | | | | |
-----------------------------------------------------------------
In the case of the shifting of a memory area:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-----------------------------------------------------------------
|15 |14 |13 |12 |11 |10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|---|---|-----------|-----------|
| 1 | 1 | 1 | 0 | 0 | 0 | 0 |dr | 1 | 1 | MODE | REGISTER |
----------------------------------------=========================
<ea>
NUMBER/REGISTER
Specifies number of shifting or number of register which contents
the number of shifting.
If i/r = 0, number of shifting is specified in the instruction as
immediate data
If i/r = 1, it's specified in the data register.
If dr = 0, right shifting
If dr = 1, left shifting
SIZE
00->one Byte operation
01->one Word operation
10->one Long operation
REGISTER
For a register shifting:
Indicates the number of data register on which shifting is applied.
For a memory shifting:
<ea> indicates operand which should be shifted.
Only addressing modes relatives to memory are allowed:
--------------------------------- -------------------------------
|Addressing Mode|Mode| Register | |Addressing Mode|Mode|Register|
|-------------------------------| |-----------------------------|
| Dn | - | - | | Abs.W |111 | 000 |
|-------------------------------| |-----------------------------|
| An | - | - | | Abs.L |111 | 001 |
|-------------------------------| |-----------------------------|
| (An) |010 |N° reg. An| | (d16,PC) | - | - |
|-------------------------------| |-----------------------------|
| (An)+ |011 |N° reg. An| | (d8,PC,Xi) | - | - |
|-------------------------------| |-----------------------------|
| -(An) |100 |N° reg. An| | (bd,PC,Xi) | - | - |
|-------------------------------| |-----------------------------|
| (d16,An) |101 |N° reg. An| |([bd,PC,Xi],od)| - | - |
|-------------------------------| |-----------------------------|
| (d8,An,Xi) |110 |N° reg. An| |([bd,PC],Xi,od)| - | - |
|-------------------------------| |-----------------------------|
| (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 - Set according to the list bit shifted out of the operand.
Unaffected for a shift count of zero.
N - Set if the most-significant bit of the result is set. Cleared
otherwise.
Z - Set if the result is zero. Cleared otherwise.
V - Set if the most significant bit is changed at any time during
the shift operation. Cleared otherwise.
C - Set according to the list bit shifted out of the operand.
Cleared for a shift count of zero.
SEE ALSO
ROd ROXd