# CHecK bounds

```NAME
CHK -- Check bounds

SYNOPSIS
CHK	<ea>,Dn

Size = (Word)
Size = (Word, Long)	(68020+)

FUNCTION
Compares the value in the data register specified to zero and to the
upper bound. The upper bound is a twos complement integer. If the
register value is less than zero or greater than the upper bound,
a CHK instruction, vector number 6, occurs.

FORMAT
-----------------------------------------------------------------
|15 |14 |13 |12 |11 |10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|-----------|-------|---|-----------|-----------|
| 0 | 1 | 0 | 0 |  REGISTER |  SIZE | 0 |    MODE   | REGISTER  |
----------------------------------------=========================
<ea>

REGISTER
<ea> specifies upper bound, addressing modes allowed are:
--------------------------------- -------------------------------
|-------------------------------| |-----------------------------|
|      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|
---------------------------------

SIZE
11->one Word operation
10->one Long operation

RESULT
X - Not affected
N - Set if Dn < 0; cleared if Dn > <ea>. Undefined otherwise.
Z - Undefined.
V - Undefined.
C - Undefined.