ST20-C1 STMICROELECTRONICS [STMicroelectronics], ST20-C1 Datasheet - Page 66

• Manufacturer Part Number: ST20-C1
• Description: Instruction Set Reference Manual
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

5.7 Data formats
A Q15 value in a 16-bit field is organiz ed as shown in Figure 5.7.
The minimum and maximum representable values are as shown in Table 5.9.
5.7.5
When a Q15 value is stored in an oversized field, e .g.a 32-bit register, the significant
bits are placed at the least significant end of the field, and the v alue is sign-extended
to the width of the whole field.
The value still has the same range (-1
bits.
A Q15 value in a 32-bit field is organiz ed as shown in Figure 5.8.
The minimum and maximum representable values are as shown in Table 5.10.
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Bit position
Q15 in an oversized field
Bit position
-(2
Most significant
31
0
sign bit
)
-(2
30
0
-(2
)
Most significant
15
sign extended
-(2
0
sign bit
29
)
Maximum
Minimum
Figure 5.7 Q15 data format (16-bits)
0
Figure 5.8 Q15 data format (32-bits)
)
binary point
2
14
-1
Table 5.9 Q15 limiting values
2
13
-2
2
12
-3
Hex Value
-(2
16
7FFF
8000
0
n < 1) and the same number of significant
)
-(2
15
0
)
binary point
2
14
Decimal Value
-1
+0.9999
-1
Basic Q15 value
Least significant
2
-14
1
2
Least significant
2
2
-13
0
-15
2
-14
1
2
-15
0