| 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 can only 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
REGISTER | dr | SIZE | i/r | 0 | 0 | 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 allowed are:
| Addressing Mode | Mode | Register |
|---|
| Dn | - | - |
| An | - | - |
| (An) | 010 | No reg. An |
| (An)+ | 011 | No reg. An |
| -(An) | 100 | No reg. An |
| (d16,An) | 101 | No reg. An |
| (d8,An,Xi) | 110 | No reg. An |
| (bd,An,Xi) | 110 | No reg. An |
| ([bd,An,Xi]od) | 110 | No reg. An |
| ([bd,An],Xi,od) | 110 | No reg. An |
|
| Addressing Mode | Mode | Register |
|---|
| Abs.W | 111 | 000 |
| Abs.L | 111 | 001 |
| (d16,PC) | - | - |
| (d8,PC,Xi) | - | - |
| (bd,PC,Xi) | - | - |
| ([bd,PC,Xi],od) | - | - |
| ([bd,PC],Xi,od) | - | - |
| #data | - | - |
|
|
| 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. |
|
