Typewriter User Manual

MOTOROLA MC68340 USER’S MANUAL 5- 29
5.3.3.10 CONDITION TESTS. Conditional program control instructions and the TRAPcc
instruction execute on the basis of condition tests. A condition test is the evaluation of a
logical expression related to the state of the CCR bits. If the result is 1, the condition is
true. If the result is 0, the condition is false. For example, the T condition is always true,
and the EQ condition is true only if the Z-bit condition code is true. Table 5-12 lists each
condition test.
Table 5-12. Condition Tests
Mnemonic Condition Encoding Test
T True 0000 1
F* False 0001 0
HI High 0010 C • Z
LS Low or Same 0011 C + Z
CC Carry Clear 0100 C
CS Carry Set 0101 C
NE Not Equal 0110 Z
EQ Equal 0111 Z
VC Overflow Clear 1000 V
VS Overflow Set 1001 V
PL Plus 1010 N
MI Minus 1011 N
GE Greater or Equal 1100 N • V + N • V
LT Less Than 1101 N • V + N • V
GT Greater Than 1110 N • V • Z + N • V • Z
LE Less or Equal 1111 Z + N • V + N • V
* Not available for the Bcc instruction.
• = Boolean AND
+ = Boolean OR
N = Boolean NOT
5.3.4 Using the TBL Instructions
There are four TBL instructions. TBLS returns a signed, rounded byte, word, or long-word
result. TBLSN returns a signed, unrounded byte, word, or long-word result. TBLU returns
an unsigned, rounded byte, word, or long-word result. TBLUN returns an unsigned,
unrounded byte, word, or long-word result. All four instructions support two types of
interpolation data: an n-element table stored in memory and a two-element range stored in
a pair of data registers. The latter form provides a means of performing surface (3D)
interpolation between two previously calculated linear interpolations.
The following examples show how to compress tables and use fewer interpolation levels
between table entries. Example 1 (see Figure 5-7) demonstrates TBL for a 257-entry
table, allowing up to 256 interpolation levels between entries. Example 2 (see Figure 5-8)
reduces table length for the same data to four entries. Example 3 (see Figure 5-9)
demonstrates use of an 8-bit independent variable with an instruction.
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