at94k10al ATMEL Corporation, at94k10al Datasheet - Page 119

• Manufacturer Part Number: at94k10al
• Description: At94k05al 5k - 40k Gates Of At40k Fpga With 8-bit Microcontroller, Up To 36k Bytes Of Sram And On-chip Jtag Ice
• Manufacturer: ATMEL Corporation

1138I–FPSLI–1/08
Table 4-25.
Using the FMUL, FMULS and FMULSU instructions should not be more complex than the MUL,
MULS and MULSU instructions. However, one potential problem is to assign fractional variables
right values in a simple way. The fraction 0.75 (= 0.5 + 0.25) will, for example, be “0110 0000” if
8 bits are used.
To convert a positive fractional number in the range [0, 2> (for example 1.8125) to the format
used in the AVR, the following algorithm, illustrated by an example, should be used:
Is there a “1” in the number?
Yes, 1.8125 is higher than or equal to 1.
Is there a “0.5” in the rest?
Yes, 1.625 is higher than or equal to 1.
Byte is now “11xx xxxx”
Is there a “0.25” in the rest?
Yes, 1.25 is higher than or equal to 1.
Is there a “0.125” in the rest?
No, 0.5 is lower than 1.
Is there a “0.0625” in the rest?
Yes, 1 is higher than or equal to 1.
Bit Number
Byte is now “1xxx xxxx”
0.8125 / 0.5 = 1.625
0.625 / 0.5 = 1.25
Byte is now “111x xxxx”
0.25 / 0.5 = 0.5
Byte is now “1110 xxxx”
0.5 / 0.5 = 1
Byte is now “1110 1xxx”
7
6
5
4
3
2
1
0
Comparison of Integer and Fractional Formats
Unsigned Integer
Bit Significance
2
2
2
2
2
2
2
2
7
6
5
4
3
2
1
0
= 64
= 128
= 32
= 16
= 8
= 4
= 2
= 1
AT94KAL Series FPSLIC
Unsigned Fractional Number
Bit Significance
2
2
2
2
2
2
2
2
0
-1
-2
-3
-4
-5
-6
-7
= 1
= 0.0078125
= 0.5
= 0.25
= 0.125
= 0.0625
= 0.3125
= 0.015625
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