MB86330 Datasheet, PDF (26/46 Pages) Fujitsu Component Limited. – 16-bit Fixed-point DSP

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 × signed 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.
15 14 13 12
S
×_S
10
16 bits
0
16 bits
SS
39 38
SS
32 31 30 29 28
17 16 15 14
Sign extension
31 bits of an operation result
0
21 0
40 bits
• Fixed-point type multiplication (signed data × unsigned data)
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.
15 14 13 12
S
×
10
S
SS
39
33 32 31 30 29 28
17 16 15 14
Sign extension
32 bits of an operation result
16 bits
0 16 bits
0
21 0
40 bits
• Fixed-point type multiplication (unsigned data × unsigned data)
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.
15 14 13 12
10
×
0
0
39
33 32 31 30 29 28
17 16 15 14
0 is set.
32 bits of an operation result
16 bits
0 ^{16 bits}
0
21 0
40 bits
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