Stratix GX Architecture
Table 4–13 shows the summary of input register modes for the DSP block.
Table 4–13. Input Register Modes
Register Input Mode
Parallel input
9 × 9
v
v
18 × 18
v
v
36 × 36
v
Shift register input
Multiplier
The multiplier supports 9 × 9-, 18 × 18-, or 36 × 36-bit multiplication. Each
DSP block supports eight possible 9 × 9-bit or smaller multipliers. There
are four multiplier blocks available for multipliers larger than 9 × 9 bits
but smaller than 18 × 18 bits. There is one multiplier block available for
multipliers larger than 18 × 18 bits but smaller than or equal to 36 × 36 bits.
The ability to have several small multipliers is useful in applications such
as video processing. Large multipliers greater than 18 × 18 bits are useful
for applications such as the mantissa multiplication of a single-precision
floating-point number.
The multiplier operands can be signed or unsigned numbers, where the
result is signed if either input is signed as shown in Table 4–14. The
sign_aand sign_bsignals provide dynamic control of each operand’s
representation: a logic 1 indicates the operand is a signed number, a logic
0 indicates the operand is an unsigned number. These sign signals affect
all multipliers and adders within a single DSP block and you can register
them to match the data path pipeline. The multipliers are full precision
(that is, 18 bits for the 18-bit multiply, 36-bits for the 36-bit multiply, and
so on), regardless of whether sign_aor sign_bset the operands as
signed or unsigned numbers.
Table 4–14. Multiplier Signed Representation
Data A
Data B
Result
Unsigned
Unsigned
Signed
Unsigned
Signed
Unsigned
Signed
Signed
Signed
Unsigned
Signed
Signed
Altera Corporation
February 2005
4–55
Stratix GX Device Handbook, Volume 1
ALTERA [ ALTERA CORPORATION ]
