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NAME
DIVU, DIVUL -- Unsigned divide
SYNOPSIS
DIVU.W <ea>,Dn 32/16 -> 16r:16q
DIVU.L <ea>,Dq 32/32 -> 32q (68020+)
DIVU.L <ea>,Dr:Dq 64/32 -> 32r:32q (68020+)
DIVUL.L <ea>,Dr:Dq 32/32 -> 32r:32q (68020+)
Size = (Word, Long)
FUNCTION
Divides the unsigned destination operand by the unsigned
source operand and stores the unsigned result in the destination.
The instruction has a word form and three long forms. For the
word form, the destination operand is a long word and the source
operand is a word. The resultant quotient is placed in the lower
word of the destination and the resultant remainder is placed in the
upper word of the destination. The sign of the remainder is the
same as the sign of the dividend.
In the first long form, the destination and the source are both
long words. The quotient is placed in the longword of the destination
and the remainder is discarded.
The second long form has the destination as a quadword (eight bytes),
specified by any two data registers, and the source is a long word.
The resultant remainder and quotient are both long words and are
placed in the destination registers.
The final long form has both the source and the destination as long
words and the resultant quotient and remainder as long words.
FORMAT
In the case of DIVU.W:
~~~~~~~~~~~~~~~~~~~~~ <ea>
----------------------------------------=========================
|15 |14 |13 |12 |11 |10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|-----------|---|---|---|-----------|-----------|
| 1 | 0 | 0 | 0 | REGISTER | 0 | 1 | 1 | MODE | REGISTER |
-----------------------------------------------------------------
"REGISTER" indicates the number of data register.
In the case of DIVU.L and of DIVUL.L:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <ea>
-----------------------------------------=========================
|15 |14 |13 |12 |11 |10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|----|---|---|---|---|-----------|-----------|
| 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | MODE | REGISTER |
|---|-----------|---|----|---|---|---|---|-----------|-----------|
| 0 |Dq REGISTER| 0 |SIZE| 0 | 0 | 0 | 0 | 0 | 0 | 0 |Dr REGISTER|
------------------------------------------------------------------
"Dq REGISTER" indicates the number of data register for destination
operand. This register first contains 32 bits of low weight of
dividend, and after the value of quotient on 32 bits.
"SIZE" specifies if dividend is on 32 or 64 bits:
0-> 32 bits dividend placed in Dq.
1-> 64 bits dividend placed in Dr:Dq.
"Dr REGISTER" indicates the number of data register for destination
operand. This register first contains 32 bits of upper weight of
dividend if "SIZE" = 1, and after the value of rest on 32 bits.
If Dr and Dq represents the same register, only quotient on 32 bits
is put in Dq.
<ea> field specifies source operand, allowed addressing modes are:
--------------------------------- -------------------------------
|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)+ |011 |N° reg. An| | (d8,PC,Xi) |111 | 011 |
|-------------------------------| |-----------------------------|
| -(An) |100 |N° reg. 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 |111 | 100 |
|-------------------------------| -------------------------------
|([bd,An,Xi]od) |110 |N° reg. An|
|-------------------------------|
|([bd,An],Xi,od)|110 |N° reg. An|
---------------------------------
RESULT
X - Not affected
N - See below.
Z - Set if the quotient is zero, cleared otherwise. Undefined if
overflow or divide by zero occurs.
V - Set if overflow occurs, cleared otherwise. Undefined if divide by
zero occurs.
C - Always cleared.
Notes:
1. If divide by zero occurs, an exception occurs.
2. If overflow occurs, neither operand is affected.
According to the Motorola data books, the N flag is set if the
quotient is negative, but in an unsigned divide, this seems to
be impossible.
SEE ALSO
DIVS MULS MULU