MB86330 Fujitsu Media Devices Limited, MB86330 Datasheet - Page 26

• Manufacturer Part Number: MB86330
• Description: 16-bit Fixed-point DSP
• Manufacturer: Fujitsu Media Devices Limited

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MB86330
2. Multiplication in Fixed-point Type Mode
With the “ITG” bit in the status register set at 0, fixed-point type mode is set up, and multiplication is executed
in the following format. You can use ordinary mode and NOG mode in which the guard bit is not used.
(1) Ordinary Mode
• Fixed-point type multiplication (signed data
• Fixed-point type multiplication (signed data
• Fixed-point type multiplication (unsigned data
31 bits of the result of a signed operation are stored into bits 1 to 31 in the accumulator shifted to the left by
one bit. “0” is set to bit 0, with the same value as at bit 31 set to bits 32 to 39.
32 bits of the result of a signed operation are stored into bits 1 to 32 in the accumulator shifted to the left by
one bit. “0” is set to bit 0, with the same value as at bit 32 set to bits 33 to 39.
32 bits of the result of an unsigned operation are stored into bits 1 to 32 in the accumulator shifted to the left
by one bit. “0” is set to bit 0, and bits 33 to 39.
39 38
39
39
S
S
Sign extension
Sign extension
0
0 is set.
S
33 32 31 30 29 28
33 32 31 30 29 28
S
0
32 31 30 29
S
S
15 14 13 12
15 14 13 12
15 14 13 12
S
S
S
S
28
32 bits of an operation result
31 bits of an operation result
32 bits of an operation result
signed data)
unsigned data)
unsigned data)
17 16 15 14
17 16 15 14
17 16 15 14
1
1
1
0
0
0
2
2
2
1
1
1
0
0
0
0
0
0
0
0
0
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16 bits
16 bits
40 bits
16 bits
16 bits
40 bits
16 bits
16 bits
40 bits